diff --git a/harness/iteratorZipUtils.js b/harness/iteratorZipUtils.js
new file mode 100644
index 0000000000..05e6c0f04d
--- /dev/null
+++ b/harness/iteratorZipUtils.js
@@ -0,0 +1,223 @@
+// Copyright (C) 2025 André Bargull.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+description: |
+    Utility functions for testing Iterator.prototype.zip and Iterator.prototype.zipKeyed. Requires inclusion of propertyHelper.js.
+defines:
+  - forEachSequenceCombination
+  - forEachSequenceCombinationKeyed
+  - assertZipped
+  - assertZippedKeyed
+  - assertIteratorResult
+  - assertIsPackedArray
+---*/
+
+// Assert |result| is an object created by CreateIteratorResultObject.
+function assertIteratorResult(result, value, done, label) {
+  assert.sameValue(
+    Object.getPrototypeOf(result),
+    Object.prototype,
+    label + ": [[Prototype]] of iterator result is Object.prototype"
+  );
+
+  assert(Object.isExtensible(result), label + ": iterator result is extensible");
+
+  var ownKeys = Reflect.ownKeys(result);
+  assert.compareArray(ownKeys, ["value", "done"], label + ": iterator result properties");
+
+  verifyProperty(result, "value", {
+    value: value,
+    writable: true,
+    enumerable: true,
+    configurable: true,
+  });
+
+  verifyProperty(result, "done", {
+    value: done,
+    writable: true,
+    enumerable: true,
+    configurable: true,
+  });
+}
+
+// Assert |array| is a packed array with default property attributes.
+function assertIsPackedArray(array, label) {
+  assert(Array.isArray(array), label + ": array is an array exotic object");
+
+  assert.sameValue(
+    Object.getPrototypeOf(array),
+    Array.prototype,
+    label + ": [[Prototype]] of array is Array.prototype"
+  );
+
+  assert(Object.isExtensible(array), label + ": array is extensible");
+
+  // Ensure "length" property has its default property attributes.
+  verifyProperty(array, "length", {
+    writable: true,
+    enumerable: false,
+    configurable: false,
+  });
+
+  // Ensure no holes and all elements have the default property attributes.
+  for (var i = 0; i < array.length; i++) {
+    verifyProperty(array, i, {
+      writable: true,
+      enumerable: true,
+      configurable: true,
+    });
+  }
+}
+
+// Assert |array| is an extensible null-prototype object with default property attributes.
+function _assertIsNullProtoMutableObject(object, label) {
+  assert.sameValue(
+    Object.getPrototypeOf(object),
+    null,
+    label + ": [[Prototype]] of object is null"
+  );
+
+  assert(Object.isExtensible(object), label + ": object is extensible");
+
+  // Ensure all properties have the default property attributes.
+  var keys = Object.getOwnPropertyNames(object);
+  for (var i = 0; i < keys.length; i++) {
+    verifyProperty(object, keys[i], {
+      writable: true,
+      enumerable: true,
+      configurable: true,
+    });
+  }
+}
+
+// Assert that the `zipped` iterator results as for Iterator.zip for the first `count` elements.
+// Assumes inputs is an array of arrays of length >= count.
+// Advances `zipped` by `count` steps.
+function assertZipped(zipped, inputs, count, label) {
+  // Last returned elements array.
+  var last = null;
+
+  for (var i = 0; i < count; i++) {
+    var itemLabel = label + ", step " + i;
+
+    var result = zipped.next();
+    var value = result.value;
+
+    // Test IteratorResult structure.
+    assertIteratorResult(result, value, false, itemLabel);
+
+    // Ensure value is a new array.
+    assert.notSameValue(value, last, itemLabel + ": returns a new array");
+    last = value;
+
+    // Ensure all array elements have the expected value.
+    var expected = inputs.map(function (array) {
+      return array[i];
+    });
+    assert.compareArray(value, expected, itemLabel + ": values");
+
+    // Ensure value is a packed array with default data properties.
+    //
+    // This operation is destructive, so it has to happen last.
+    assertIsPackedArray(value, itemLabel);
+  }
+}
+
+// Assert that the `zipped` iterator results as for Iterator.zipKeyed for the first `count` elements.
+// Assumes inputs is an object whose values are arrays of length >= count.
+// Advances `zipped` by `count` steps.
+function assertZippedKeyed(zipped, inputs, count, label) {
+  // Last returned elements array.
+  var last = null;
+
+  var expectedKeys = Object.keys(inputs);
+
+  for (var i = 0; i < count; i++) {
+    var itemLabel = label + ", step " + i;
+
+    var result = zipped.next();
+    var value = result.value;
+
+    // Test IteratorResult structure.
+    assertIteratorResult(result, value, false, itemLabel);
+
+    // Ensure resulting object is a new object.
+    assert.notSameValue(value, last, itemLabel + ": returns a new object");
+    last = value;
+
+    // Ensure resulting object has the expected keys and values.
+    assert.compareArray(Reflect.ownKeys(value), expectedKeys, itemLabel + ": result object keys");
+
+    var expectedValues = Object.values(inputs).map(function (array) {
+      return array[i];
+    });
+    assert.compareArray(Object.values(value), expectedValues, itemLabel + ": result object values");
+
+    // Ensure resulting object is a null-prototype mutable object with default data properties.
+    //
+    // This operation is destructive, so it has to happen last.
+    _assertIsNullProtoMutableObject(value, itemLabel);
+  }
+}
+
+function forEachSequenceCombinationKeyed(callback) {
+  return forEachSequenceCombination(function(inputs, inputsLabel, min, max) {
+    var object = {};
+    for (var i = 0; i < inputs.length; ++i) {
+      object["prop_" + i] = inputs[i];
+    }
+    inputsLabel = "inputs = " + JSON.stringify(object);
+    callback(object, inputsLabel, min, max);
+  });
+}
+
+function forEachSequenceCombination(callback) {
+  function test(inputs) {
+    if (inputs.length === 0) {
+      callback(inputs, "inputs = []", 0, 0);
+      return;
+    }
+
+    var lengths = inputs.map(function(array) {
+      return array.length;
+    });
+
+    var min = Math.min.apply(null, lengths);
+    var max = Math.max.apply(null, lengths);
+
+    var inputsLabel = "inputs = " + JSON.stringify(inputs);
+
+    callback(inputs, inputsLabel, min, max);
+  }
+
+  // Yield all prefixes of the string |s|.
+  function* prefixes(s) {
+    for (var i = 0; i <= s.length; ++i) {
+      yield s.slice(0, i);
+    }
+  }
+
+  // Zip an empty iterable.
+  test([]);
+
+  // Zip a single iterator.
+  for (var prefix of prefixes("abcd")) {
+    test([prefix.split("")]);
+  }
+
+  // Zip two iterators.
+  for (var prefix1 of prefixes("abcd")) {
+    for (var prefix2 of prefixes("efgh")) {
+      test([prefix1.split(""), prefix2.split("")]);
+    }
+  }
+
+  // Zip three iterators.
+  for (var prefix1 of prefixes("abcd")) {
+    for (var prefix2 of prefixes("efgh")) {
+      for (var prefix3 of prefixes("ijkl")) {
+        test([prefix1.split(""), prefix2.split(""), prefix3.split("")]);
+      }
+    }
+  }
+}
diff --git a/test/built-ins/Iterator/zip/basic-longest.js b/test/built-ins/Iterator/zip/basic-longest.js
new file mode 100644
index 0000000000..c74895e8e2
--- /dev/null
+++ b/test/built-ins/Iterator/zip/basic-longest.js
@@ -0,0 +1,85 @@
+// Copyright (C) 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zip
+description: >
+  Basic Iterator.zip test with "longest" mode.
+includes: [compareArray.js, propertyHelper.js, iteratorZipUtils.js]
+features: [joint-iteration]
+---*/
+
+function testSequence(inputs, inputsLabel, minLength, maxLength) {
+  function test(options, optionsLabel, getPaddingForInput) {
+    var label = optionsLabel + ", " + inputsLabel;
+    var it = Iterator.zip(inputs, options);
+    assertZipped(it, inputs, minLength, label);
+
+    for (var i = minLength; i < maxLength; i++) {
+      var itemLabel = label + ", step " + i;
+
+      var result = it.next();
+      var value = result.value;
+
+      // Test IteratorResult structure.
+      assertIteratorResult(result, value, false, itemLabel);
+
+      var expected = inputs.map(function (input, j) {
+        return i < input.length ? input[i] : getPaddingForInput(j);
+      });
+      assert.compareArray(value, expected, itemLabel + ": values");
+    }
+    assertIteratorResult(it.next(), undefined, true, label + ": after completion");
+  }
+
+  test(
+    { mode: "longest" },
+    "options = { mode: 'longest' }",
+    function () {
+      return undefined;
+    },
+  );
+
+  test(
+    { mode: "longest", padding: [] },
+    "options = { mode: 'longest', padding: [] }",
+    function () {
+      return undefined;
+    },
+  );
+
+  test(
+    { mode: "longest", padding: ["pad"] },
+    "options = { mode: 'longest', padding: ['pad'] }",
+    function (idx) {
+      return idx === 0 ? "pad" : undefined;
+    },
+  );
+
+  test(
+    { mode: "longest", padding: Array(inputs.length).fill("pad") },
+    "options = { mode: 'longest', padding: ['pad', 'pad', ..., 'pad'] }",
+    function (idx) {
+      return "pad";
+    },
+  );
+
+  // Yield an infinite amount of numbers.
+  var numbers = {
+    *[Symbol.iterator]() {
+      var i = 0;
+      while (true) {
+        yield 100 + i++;
+      }
+    }
+  };
+  test(
+    { mode: "longest", padding: numbers },
+    "options = { mode: 'longest', padding: numbers }",
+    function (idx) {
+      return 100 + idx;
+    },
+  );
+}
+
+forEachSequenceCombination(testSequence);
diff --git a/test/built-ins/Iterator/zip/basic-shortest.js b/test/built-ins/Iterator/zip/basic-shortest.js
new file mode 100644
index 0000000000..8487c0fe7e
--- /dev/null
+++ b/test/built-ins/Iterator/zip/basic-shortest.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zip
+description: >
+  Basic Iterator.zip test with "shortest" mode.
+includes: [compareArray.js, propertyHelper.js, iteratorZipUtils.js]
+features: [joint-iteration]
+---*/
+
+function testSequence(inputs, inputsLabel, minLength, maxLength) {
+  function test(options, optionsLabel) {
+    var label = optionsLabel + ", " + inputsLabel;
+    var it = Iterator.zip(inputs, options);
+    assertZipped(it, inputs, minLength, label);
+
+    // Iterator is closed after `minLength` items.
+    assertIteratorResult(it.next(), undefined, true, label + ": after completion");
+  }
+
+  test(undefined, "options = undefined");
+
+  test({}, "options = {}");
+
+  test({ mode: "shortest" }, "options = { mode: 'shortest' }");
+}
+
+forEachSequenceCombination(testSequence);
diff --git a/test/built-ins/Iterator/zip/basic-strict.js b/test/built-ins/Iterator/zip/basic-strict.js
new file mode 100644
index 0000000000..d41ec7e56b
--- /dev/null
+++ b/test/built-ins/Iterator/zip/basic-strict.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zip
+description: >
+  Basic Iterator.zip test with "strict" mode.
+includes: [compareArray.js, propertyHelper.js, iteratorZipUtils.js]
+features: [joint-iteration]
+---*/
+
+function testSequence(inputs, inputsLabel, minLength, maxLength) {
+  function test(options, optionsLabel) {
+    var label = optionsLabel + ", " + inputsLabel;
+    var it = Iterator.zip(inputs, options);
+    assertZipped(it, inputs, minLength, label);
+
+    if (minLength === maxLength) {
+      assertIteratorResult(it.next(), undefined, true, label + ": after completion");
+    } else {
+      assert.throws(TypeError, function() {
+        it.next();
+      }, label + " should throw after " + minLength + " items.");
+    }
+  }
+
+  test({ mode: "strict" }, "options = { mode: 'strict' }");
+}
+
+forEachSequenceCombination(testSequence);
diff --git a/test/built-ins/Iterator/zip/basic.js b/test/built-ins/Iterator/zip/basic.js
deleted file mode 100644
index a11102ccbe..0000000000
--- a/test/built-ins/Iterator/zip/basic.js
+++ /dev/null
@@ -1,236 +0,0 @@
-// Copyright (C) 2025 André Bargull. All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-esid: sec-iterator.zip
-description: >
-  Basic Iterator.zip test using all three possible modes.
-includes: [compareArray.js, propertyHelper.js]
-features: [joint-iteration]
----*/
-
-// Assert |result| is an object created by CreateIteratorResultObject.
-function assertIteratorResult(result, value, done) {
-  assert.sameValue(
-    Object.getPrototypeOf(result),
-    Object.prototype,
-    "[[Prototype]] of iterator result is Object.prototype"
-  );
-
-  assert(Object.isExtensible(result), "iterator result is extensible");
-
-  var ownKeys = Reflect.ownKeys(result);
-  assert.sameValue(ownKeys.length, 2, "iterator result has two own properties");
-  assert.sameValue(ownKeys[0], "value", "first property is 'value'");
-  assert.sameValue(ownKeys[1], "done", "second property is 'done'");
-
-  verifyProperty(result, "value", {
-    value: value,
-    writable: true,
-    enumerable: true,
-    configurable: true,
-  });
-
-  verifyProperty(result, "done", {
-    value: done,
-    writable: true,
-    enumerable: true,
-    configurable: true,
-  });
-}
-
-// Assert |array| is a packed array with default property attributes.
-function assertIsPackedArray(array) {
-  assert(Array.isArray(array), "array is an array exotic object");
-
-  assert.sameValue(
-    Object.getPrototypeOf(array),
-    Array.prototype,
-    "[[Prototype]] of array is Array.prototype"
-  );
-
-  assert(Object.isExtensible(array), "array is extensible");
-
-  // Ensure "length" property has its default property attributes.
-  verifyProperty(array, "length", {
-    writable: true,
-    enumerable: false,
-    configurable: false,
-  });
-
-  // Ensure no holes and all elements have the default property attributes.
-  for (var i = 0; i < array.length; i++) {
-    verifyProperty(array, i, {
-      writable: true,
-      enumerable: true,
-      configurable: true,
-    });
-  }
-}
-
-// Yield all prefixes of the string |s|.
-function* prefixes(s) {
-  for (var i = 0; i <= s.length; ++i) {
-    yield s.slice(0, i);
-  }
-}
-
-// Empty iterable doesn't yield any values.
-var empty = {
-  *[Symbol.iterator]() {
-  }
-};
-
-// Yield a single value.
-var single = {
-  *[Symbol.iterator]() {
-    yield 1000;
-  }
-};
-
-// Yield an infinite amount of numbers.
-var numbers = {
-  *[Symbol.iterator]() {
-    var i = 0;
-    while (true) {
-      yield 100 + i++;
-    }
-  }
-};
-
-// |iterables| is an array whose elements are array(-like) objects. Pass it as
-// the "iterables" argument to |Iterator.zip|, using |options| as the "options"
-// argument.
-//
-// Then iterate over the returned |Iterator.zip| iterator and check all
-// returned iteration values have the expected values.
-function test(iterables, options) {
-  var mode = (options && options.mode) || "shortest";
-  var padding = options && options.padding;
-
-  var lengths = iterables.map(function(array) {
-    return array.length;
-  });
-
-  var min = Math.min.apply(null, lengths);
-  var max = Math.max.apply(null, lengths);
-
-  // Expected number of iterations.
-  var count;
-  switch (mode) {
-    case "shortest":
-      count = min;
-      break;
-    case "longest":
-      count = max;
-      break;
-    case "strict":
-      count = max;
-      break;
-  }
-
-  // Compute padding array when |mode| is "longest".
-  if (mode === "longest") {
-    if (padding) {
-      padding = Iterator.from(padding).take(iterables.length).toArray();
-    } else {
-      padding = [];
-    }
-
-    // Fill with undefined until there are exactly |iterables.length| elements.
-    padding = padding.concat(Array(iterables.length - padding.length).fill(undefined));
-    assert.sameValue(padding.length, iterables.length);
-  }
-
-  // Last returned elements array.
-  var last = null;
-
-  var it = Iterator.zip(iterables, options);
-  for (var i = 0; i < count; i++) {
-    // "strict" mode throws an error if number of elements don't match.
-    if (mode === "strict" && min < max && i === min) {
-      assert.throws(TypeError, function() {
-        it.next();
-      });
-      break;
-    }
-
-    var result = it.next();
-    var value = result.value;
-
-    // Test IteratorResult structure.
-    assertIteratorResult(result, value, false);
-
-    // Ensure value is a new array.
-    assert.notSameValue(value, last, "returns a new array");
-    last = value;
-
-    // Ensure all array elements have the expected value.
-    var expected = iterables.map(function(array, k) {
-      if (i < array.length) {
-        return array[i];
-      }
-      assert.sameValue(mode, "longest", "padding is only used for 'longest' mode");
-      return padding[k];
-    });
-    assert.compareArray(value, expected);
-
-    // Ensure value is a packed array with default data properties.
-    //
-    // This operation is destructive, so it has to happen last.
-    assertIsPackedArray(value);
-  }
-
-  // Iterator is closed.
-  assertIteratorResult(it.next(), undefined, true);
-}
-
-var validOptions = [
-  undefined,
-  {},
-  {mode: "shortest"},
-  {mode: "longest"},
-  {mode: "longest", padding: empty},
-  {mode: "longest", padding: single},
-  {mode: "longest", padding: numbers},
-  {mode: "strict"},
-];
-
-for (var options of validOptions) {
-  // Zip an empty iterable.
-  var it = Iterator.zip([], options);
-  assertIteratorResult(it.next(), undefined, true);
-
-  // Zip a single iterator.
-  for (var prefix of prefixes("abcd")) {
-    // Split prefix into an array.
-    test([prefix.split("")], options);
-
-    // Use String wrapper as the iterable.
-    test([new String(prefix)], options);
-  }
-
-  // Zip two iterators.
-  for (var prefix1 of prefixes("abcd")) {
-    for (var prefix2 of prefixes("efgh")) {
-      // Split prefixes into arrays.
-      test([prefix1.split(""), prefix2.split("")], options);
-
-      // Use String wrappers as the iterables.
-      test([new String(prefix1), new String(prefix2)], options);
-    }
-  }
-
-  // Zip three iterators.
-  for (var prefix1 of prefixes("abcd")) {
-    for (var prefix2 of prefixes("efgh")) {
-      for (var prefix3 of prefixes("ijkl")) {
-        // Split prefixes into arrays.
-        test([prefix1.split(""), prefix2.split(""), prefix3.split("")], options);
-
-        // Use String wrappers as the iterables.
-        test([new String(prefix1), new String(prefix2), new String(prefix3)], options);
-      }
-    }
-  }
-}
diff --git a/test/built-ins/Iterator/zip/iterables-containing-string-objects.js b/test/built-ins/Iterator/zip/iterables-containing-string-objects.js
new file mode 100644
index 0000000000..12a402e508
--- /dev/null
+++ b/test/built-ins/Iterator/zip/iterables-containing-string-objects.js
@@ -0,0 +1,17 @@
+// Copyright (C) 2025 Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zip
+description: >
+  Accepts String objects as inputs.
+includes: [compareArray.js]
+features: [joint-iteration]
+---*/
+
+var result = Array.from(Iterator.zip([Object("abc"), Object("123")]));
+
+assert.sameValue(result.length, 3);
+assert.compareArray(result[0], ["a", "1"]);
+assert.compareArray(result[1], ["b", "2"]);
+assert.compareArray(result[2], ["c", "3"]);
diff --git a/test/built-ins/Iterator/zip/iterator-non-iterable.js b/test/built-ins/Iterator/zip/iterator-non-iterable.js
new file mode 100644
index 0000000000..575a78f88d
--- /dev/null
+++ b/test/built-ins/Iterator/zip/iterator-non-iterable.js
@@ -0,0 +1,22 @@
+// Copyright (C) 2025 Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zip
+description: >
+  Throws a TypeError when the "iterables" argument is not iterable.
+features: [joint-iteration]
+---*/
+
+var invalidIterables = [
+  {},
+  { next() {}, return() {} },
+  function() {}
+];
+
+// Throws a TypeError for invalid iterables values.
+for (var iterables of invalidIterables) {
+  assert.throws(TypeError, function() {
+    Iterator.zip(iterables);
+  });
+}
diff --git a/test/built-ins/Iterator/zipKeyed/basic-longest.js b/test/built-ins/Iterator/zipKeyed/basic-longest.js
new file mode 100644
index 0000000000..2bf04ab5da
--- /dev/null
+++ b/test/built-ins/Iterator/zipKeyed/basic-longest.js
@@ -0,0 +1,105 @@
+// Copyright (C) 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zipkeyed
+description: >
+  Basic Iterator.zipKeyed test with "longest" mode.
+includes: [compareArray.js, propertyHelper.js, iteratorZipUtils.js]
+features: [joint-iteration]
+---*/
+
+function testSequence(inputs, inputsLabel, minLength, maxLength) {
+  function test(options, optionsLabel, getPaddingForInput) {
+    var label = optionsLabel + ", " + inputsLabel;
+    var it = Iterator.zipKeyed(inputs, options);
+    assertZippedKeyed(it, inputs, minLength, label);
+
+    var expectedKeys = Object.keys(inputs);
+
+    for (var i = minLength; i < maxLength; i++) {
+      var itemLabel = label + ", step " + i;
+
+      var result = it.next();
+      var value = result.value;
+
+      // Test IteratorResult structure.
+      assertIteratorResult(result, value, false, itemLabel);
+
+      // Ensure resulting object has the expected keys and values.
+      assert.compareArray(Object.keys(value), expectedKeys, itemLabel + ": result object keys");
+
+      var expectedValues = Object.values(inputs).map(function (input, j) {
+        return i < input.length ? input[i] : getPaddingForInput(j);
+      });
+      assert.compareArray(Object.values(value), expectedValues, itemLabel + ": result object values");
+    }
+    assertIteratorResult(it.next(), undefined, true, label + ": after completion");
+  }
+
+  test(
+    { mode: "longest" },
+    "options = { mode: 'longest' }",
+    function () {
+      return undefined;
+    },
+  );
+
+  test(
+    { mode: "longest", padding: {} },
+    "options = { mode: 'longest', padding: {} }",
+    function () {
+      return undefined;
+    },
+  );
+
+  test(
+    { mode: "longest", padding: { prop_0: "pad" } },
+    "options = { mode: 'longest', padding: { prop_0: 'pad' } }",
+    function (idx) {
+      return idx === 0 ? "pad" : undefined;
+    },
+  );
+
+  test(
+    { mode: "longest", padding: { prop_1: "pad" } },
+    "options = { mode: 'longest', padding: { prop_1: 'pad' } }",
+    function (idx) {
+      return idx === 1 ? "pad" : undefined;
+    },
+  );
+
+  var padding = {};
+  for (var key in inputs) {
+    padding[key] = "pad";
+  }
+  test(
+    { mode: "longest", padding: padding },
+    "options = { mode: 'longest', padding: { prop_0: 'pad', ..., prop_N: 'pad' } }",
+    function (idx) {
+      return "pad";
+    },
+  );
+
+  // Object with many properties.
+  padding = new Proxy({}, {
+    has(target, key) {
+      return key.indexOf('_') !== -1;
+    },
+    get(target, key, receiver) {
+      var split = key.split('_');
+      if (split.length !== 2) return undefined;
+      return 'pad_' + split[1];
+    }
+  });
+  test(
+    { mode: "longest", padding: padding },
+    "options = { mode: 'longest', padding: { prop_0: 'pad_1', ..., prop_N: 'pad_N' } }",
+    function (idx) {
+      return 'pad_' + idx;
+    },
+  );
+
+}
+
+forEachSequenceCombinationKeyed(testSequence);
diff --git a/test/built-ins/Iterator/zipKeyed/basic-shortest.js b/test/built-ins/Iterator/zipKeyed/basic-shortest.js
new file mode 100644
index 0000000000..b217e09c9e
--- /dev/null
+++ b/test/built-ins/Iterator/zipKeyed/basic-shortest.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zipkeyed
+description: >
+  Basic Iterator.zipkeyed test with "shortest" mode.
+includes: [compareArray.js, propertyHelper.js, iteratorZipUtils.js]
+features: [joint-iteration]
+---*/
+
+function testSequence(inputs, inputsLabel, minLength, maxLength) {
+  function test(options, optionsLabel) {
+    var label = optionsLabel + ", " + inputsLabel;
+    var it = Iterator.zipKeyed(inputs, options);
+    assertZippedKeyed(it, inputs, minLength, label);
+
+    // Iterator is closed after `minLength` items.
+    assertIteratorResult(it.next(), undefined, true, label + ": after completion");
+  }
+
+  test(undefined, "options = undefined");
+
+  test({}, "options = {}");
+
+  test({ mode: "shortest" }, "options = { mode: 'shortest' }");
+}
+
+forEachSequenceCombinationKeyed(testSequence);
diff --git a/test/built-ins/Iterator/zipKeyed/basic-strict.js b/test/built-ins/Iterator/zipKeyed/basic-strict.js
new file mode 100644
index 0000000000..52dc509835
--- /dev/null
+++ b/test/built-ins/Iterator/zipKeyed/basic-strict.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zipkeyed
+description: >
+  Basic Iterator.zipkeyed test with "strict" mode.
+includes: [compareArray.js, propertyHelper.js, iteratorZipUtils.js]
+features: [joint-iteration]
+---*/
+
+function testSequence(inputs, inputsLabel, minLength, maxLength) {
+  function test(options, optionsLabel) {
+    var label = optionsLabel + ", " + inputsLabel;
+    var it = Iterator.zipKeyed(inputs, options);
+    assertZippedKeyed(it, inputs, minLength, label);
+
+    if (minLength === maxLength) {
+      assertIteratorResult(it.next(), undefined, true, label + ": after completion");
+    } else {
+      assert.throws(TypeError, function() {
+        it.next();
+      }, label + " should throw after " + minLength + " items.");
+    }
+  }
+
+  test({ mode: "strict" }, "options = { mode: 'strict' }");
+}
+
+forEachSequenceCombinationKeyed(testSequence);
diff --git a/test/built-ins/Iterator/zipKeyed/basic.js b/test/built-ins/Iterator/zipKeyed/basic.js
deleted file mode 100644
index 768f844d52..0000000000
--- a/test/built-ins/Iterator/zipKeyed/basic.js
+++ /dev/null
@@ -1,270 +0,0 @@
-// Copyright (C) 2025 André Bargull. All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-esid: sec-iterator.zipkeyed
-description: >
-  Basic Iterator.zipKeyed test using all three possible modes.
-includes: [compareArray.js, propertyHelper.js]
-features: [joint-iteration]
----*/
-
-// Assert |result| is an object created by CreateIteratorResultObject.
-function assertIteratorResult(result, value, done) {
-  assert.sameValue(
-    Object.getPrototypeOf(result),
-    Object.prototype,
-    "[[Prototype]] of iterator result is Object.prototype"
-  );
-
-  assert(Object.isExtensible(result), "iterator result is extensible");
-
-  var ownKeys = Reflect.ownKeys(result);
-  assert.sameValue(ownKeys.length, 2, "iterator result has two own properties");
-  assert.sameValue(ownKeys[0], "value", "first property is 'value'");
-  assert.sameValue(ownKeys[1], "done", "second property is 'done'");
-
-  verifyProperty(result, "value", {
-    value: value,
-    writable: true,
-    enumerable: true,
-    configurable: true,
-  });
-
-  verifyProperty(result, "done", {
-    value: done,
-    writable: true,
-    enumerable: true,
-    configurable: true,
-  });
-}
-
-// Assert |actual| is a plain object equal to |expected| with default property attributes.
-function assertPlainObject(actual, expected) {
-  assert.sameValue(
-    Object.getPrototypeOf(actual),
-    null,
-    "[[Prototype]] of actual is null"
-  );
-
-  assert(Object.isExtensible(actual), "actual is extensible");
-
-  var actualKeys = Reflect.ownKeys(actual);
-  var expectedKeys = Reflect.ownKeys(expected);
-
-  // All expected property keys are present.
-  assert.compareArray(actualKeys, expectedKeys);
-
-  // All expected property values are equal.
-  for (var key of expectedKeys) {
-    assert.sameValue(actual[key], expected[key], "with key: " + String(key));
-  }
-
-  // Ensure all properties have the default property attributes.
-  for (var key of expectedKeys) {
-    verifyProperty(actual, key, {
-      writable: true,
-      enumerable: true,
-      configurable: true,
-    });
-  }
-}
-
-// Yield all prefixes of the string |s|.
-function* prefixes(s) {
-  for (var i = 0; i <= s.length; ++i) {
-    yield s.slice(0, i);
-  }
-}
-
-// Empty object.
-var empty = {};
-
-// Object with a single property.
-var single = {
-  a: 1000,
-};
-
-// Object with many properties.
-var numbers = new Proxy({}, {
-  has(target, key) {
-    if (typeof key === "symbol") {
-      key = key.description;
-    }
-    assert.sameValue(key.length, 1, "unsupported key length");
-    return true;
-  },
-  get(target, key, receiver) {
-    if (typeof key === "symbol") {
-      key = key.description;
-    }
-    assert.sameValue(key.length, 1, "unsupported key length");
-    return key.charCodeAt(0);
-  }
-});
-
-// |iterables| is an object whose properties are array(-like) objects. Pass it
-// as the "iterables" argument to |Iterator.zipKeyed|, using |options| as the
-// "options" argument.
-//
-// Then iterate over the returned |Iterator.zipKeyed| iterator and check all
-// returned iteration values have the expected values.
-function test(iterables, options) {
-  var mode = (options && options.mode) || "shortest";
-  var padding = options && options.padding;
-
-  // Not Object.entries to allow symbol property keys.
-  var entries = Reflect.ownKeys(iterables).map(function(key) {
-    return [key, iterables[key]];
-  });
-
-  var lengths = entries.map(function([key, array]) {
-    return array.length;
-  });
-
-  var min = Math.min.apply(null, lengths);
-  var max = Math.max.apply(null, lengths);
-
-  // Expected number of iterations.
-  var count;
-  switch (mode) {
-    case "shortest":
-      count = min;
-      break;
-    case "longest":
-      count = max;
-      break;
-    case "strict":
-      count = max;
-      break;
-  }
-
-  // Compute padding array when |mode| is "longest".
-  if (mode === "longest") {
-    padding = entries.map(function([key, array]) {
-      if (padding !== undefined && key in padding) {
-        return padding[key];
-      }
-      return undefined;
-    });
-  }
-
-  // Last returned results object.
-  var last = null;
-
-  var it = Iterator.zipKeyed(iterables, options);
-  for (var i = 0; i < count; i++) {
-    // "strict" mode throws an error if number of elements don't match.
-    if (mode === "strict" && min < max && i === min) {
-      assert.throws(TypeError, function() {
-        it.next();
-      });
-      break;
-    }
-
-    var result = it.next();
-    var value = result.value;
-
-    // Test IteratorResult structure.
-    assertIteratorResult(result, value, false);
-
-    // Ensure value is a new object.
-    assert.notSameValue(value, last, "returns a new object");
-    last = value;
-
-    var expected = Object.fromEntries(entries.map(function([key, array], k) {
-      if (i < array.length) {
-        return [key, array[i]];
-      }
-      assert.sameValue(mode, "longest", "padding is only used for 'longest' mode");
-      return [key, padding[k]];
-    }));
-
-    // Ensure all properties have the expected value.
-    // Ensure value is a plain with default data properties.
-    assertPlainObject(value, expected);
-  }
-
-  // Iterator is closed.
-  assertIteratorResult(it.next(), undefined, true);
-}
-
-var validOptions = [
-  undefined,
-  {},
-  {mode: "shortest"},
-  {mode: "longest"},
-  {mode: "longest", padding: empty},
-  {mode: "longest", padding: single},
-  {mode: "longest", padding: numbers},
-  {mode: "strict"},
-];
-
-for (var options of validOptions) {
-  // Zip an empty object.
-  var it = Iterator.zipKeyed({}, options);
-  assertIteratorResult(it.next(), undefined, true);
-
-  // Zip a single key.
-  for (var prefix of prefixes("abcd")) {
-    // Split prefix into an array.
-    test({
-      a: prefix.split(""),
-    }, options);
-    test({
-      [Symbol("a")]: prefix.split(""),
-    }, options);
-
-    // Use String wrapper as the iterable.
-    test({
-      a: new String(prefix),
-    }, options);
-  }
-
-  // Zip two keys.
-  for (var prefix1 of prefixes("abcd")) {
-    for (var prefix2 of prefixes("efgh")) {
-      // Split prefixes into arrays.
-      test({
-        a: prefix1.split(""),
-        b: prefix2.split(""),
-      }, options);
-      test({
-        [Symbol("a")]: prefix1.split(""),
-        [Symbol("b")]: prefix2.split(""),
-      }, options);
-
-      // Use String wrappers as the iterables.
-      test({
-        a: new String(prefix1),
-        b: new String(prefix2),
-      }, options);
-    }
-  }
-
-  // Zip three keys.
-  for (var prefix1 of prefixes("abcd")) {
-    for (var prefix2 of prefixes("efgh")) {
-      for (var prefix3 of prefixes("ijkl")) {
-        // Split prefixes into arrays.
-        test({
-          a: prefix1.split(""),
-          b: prefix2.split(""),
-          c: prefix3.split(""),
-        }, options);
-        test({
-          [Symbol("a")]: prefix1.split(""),
-          [Symbol("b")]: prefix2.split(""),
-          [Symbol("c")]: prefix3.split(""),
-        }, options);
-
-        // Use String wrappers as the iterables.
-        test({
-          a: new String(prefix1),
-          b: new String(prefix2),
-          c: new String(prefix3),
-        }, options);
-      }
-    }
-  }
-}
diff --git a/test/built-ins/Iterator/zipKeyed/iterables-containing-string-objects.js b/test/built-ins/Iterator/zipKeyed/iterables-containing-string-objects.js
new file mode 100644
index 0000000000..3ca694ca6c
--- /dev/null
+++ b/test/built-ins/Iterator/zipKeyed/iterables-containing-string-objects.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2025 Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zipKeyed
+description: >
+  Accepts String objects as inputs.
+includes: [compareArray.js]
+features: [joint-iteration]
+---*/
+
+var result = Array.from(Iterator.zipKeyed({
+  a: Object("abc"),
+  b: Object("123"),
+}));
+
+assert.sameValue(result.length, 3);
+result.forEach(function (object) {
+  assert.compareArray(Object.keys(object), ["a", "b"]);
+});
+assert.compareArray(Object.values(result[0]), ["a", "1"]);
+assert.compareArray(Object.values(result[1]), ["b", "2"]);
+assert.compareArray(Object.values(result[2]), ["c", "3"]);
diff --git a/test/built-ins/Iterator/zipKeyed/iterables-iteration-enumerable.js b/test/built-ins/Iterator/zipKeyed/iterables-iteration-enumerable.js
index 86d2dc2cf4..cddbadab7b 100644
--- a/test/built-ins/Iterator/zipKeyed/iterables-iteration-enumerable.js
+++ b/test/built-ins/Iterator/zipKeyed/iterables-iteration-enumerable.js
@@ -38,7 +38,7 @@ var iterables = Object.create(null, {
         enumerable: false,
       });
 
-      return [];
+      return ['value for b'];
     }
   },
   c: {
@@ -58,7 +58,7 @@ var iterables = Object.create(null, {
         enumerable: true,
       });
 
-      return [];
+      return ['value for d'];
     }
   },
   e: {
@@ -66,15 +66,19 @@ var iterables = Object.create(null, {
     configurable: true,
     get() {
       log.push("get e");
-      return [];
+      return ['value for e'];
     }
   },
 });
 
-Iterator.zipKeyed(iterables);
+var result = Array.from(Iterator.zipKeyed(iterables));
 
 assert.compareArray(log, [
   "get b",
   "get d",
   "get e",
 ]);
+
+assert.sameValue(result.length, 1);
+assert.compareArray(Object.keys(result[0]), ["b", "d", "e"]);
+assert.compareArray(Object.values(result[0]), ["value for b", "value for d", "value for e"]);
diff --git a/test/built-ins/Iterator/zipKeyed/iterables-iteration-inherited.js b/test/built-ins/Iterator/zipKeyed/iterables-iteration-inherited.js
new file mode 100644
index 0000000000..15e49691cb
--- /dev/null
+++ b/test/built-ins/Iterator/zipKeyed/iterables-iteration-inherited.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2025 Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zipkeyed
+description: >
+  Inherited properties are skipped in "iterables" iteration.
+includes: [compareArray.js]
+features: [joint-iteration]
+---*/
+
+var parent = {
+  get a() {
+    throw new Test262Error("inherited properties should not be examined");
+  },
+}
+
+var iterables = {
+  __proto__: parent,
+  b: ['value for b'],
+};
+
+var result = Array.from(Iterator.zipKeyed(iterables));
+
+assert.sameValue(result.length, 1);
+assert.compareArray(Object.keys(result[0]), ["b"]);
+assert.compareArray(Object.values(result[0]), ["value for b"]);
diff --git a/test/built-ins/Iterator/zipKeyed/iterables-iteration-symbol-key.js b/test/built-ins/Iterator/zipKeyed/iterables-iteration-symbol-key.js
new file mode 100644
index 0000000000..e6b5ce911a
--- /dev/null
+++ b/test/built-ins/Iterator/zipKeyed/iterables-iteration-symbol-key.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2025 Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zipkeyed
+description: >
+  Symbol properties are used during "iterables" iteration.
+includes: [compareArray.js]
+features: [joint-iteration]
+---*/
+
+var symbolA = Symbol('a');
+
+var iterables = {
+  [symbolA]: ['value for a'],
+  b: ['value for b'],
+};
+
+var result = Array.from(Iterator.zipKeyed(iterables));
+
+assert.sameValue(result.length, 1);
+assert.compareArray(Reflect.ownKeys(result[0]), ["b", symbolA]);
+assert.sameValue(result[0].b, "value for b");
+assert.sameValue(result[0][symbolA], "value for a");
diff --git a/test/built-ins/Iterator/zipKeyed/iterables-iteration-undefined.js b/test/built-ins/Iterator/zipKeyed/iterables-iteration-undefined.js
new file mode 100644
index 0000000000..6a7bec78ef
--- /dev/null
+++ b/test/built-ins/Iterator/zipKeyed/iterables-iteration-undefined.js
@@ -0,0 +1,22 @@
+// Copyright (C) 2025 Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-iterator.zipkeyed
+description: >
+  undefined-valued properties are skipped in "iterables" iteration.
+includes: [compareArray.js]
+features: [joint-iteration]
+---*/
+
+
+var iterables = {
+  a: undefined,
+  b: ['value for b'],
+};
+
+var result = Array.from(Iterator.zipKeyed(iterables));
+
+assert.sameValue(result.length, 1);
+assert.compareArray(Reflect.ownKeys(result[0]), ["b"]);
+assert.compareArray(Object.values(result[0]), ["value for b"]);
diff --git a/test/built-ins/Iterator/zipKeyed/iterables-iteration.js b/test/built-ins/Iterator/zipKeyed/iterables-iteration.js
index 7b960622b6..7890602742 100644
--- a/test/built-ins/Iterator/zipKeyed/iterables-iteration.js
+++ b/test/built-ins/Iterator/zipKeyed/iterables-iteration.js
@@ -42,11 +42,6 @@ var iterableReturningThrowingIterator = {
   }
 };
 
-// |undefined| values are ignored.
-Iterator.zipKeyed({
-  a: undefined,
-});
-
 // GetIteratorFlattenable accepts both iterables and iterators.
 Iterator.zipKeyed({
   a: throwingIterator,
@@ -61,6 +56,7 @@ var badIterators = [
   Symbol(),
   0,
   0n,
+  // undefined is handled separately
 ];
 
 for (var iterator of badIterators) {