diff --git a/packages/zone.js/lib/browser/property-descriptor.ts b/packages/zone.js/lib/browser/property-descriptor.ts
index e0f7b5482a5..1db4d6a3f01 100644
--- a/packages/zone.js/lib/browser/property-descriptor.ts
+++ b/packages/zone.js/lib/browser/property-descriptor.ts
@@ -10,14 +10,7 @@
  * @suppress {globalThis}
  */
 
-import {
-  isBrowser,
-  isIE,
-  isMix,
-  isNode,
-  ObjectGetPrototypeOf,
-  patchOnProperties,
-} from '../common/utils';
+import {isBrowser, isMix, isNode, ObjectGetPrototypeOf, patchOnProperties} from '../common/utils';
 
 export interface IgnoreProperty {
   target: any;
@@ -34,7 +27,7 @@ export function filterProperties(
   }
 
   const tip: IgnoreProperty[] = ignoreProperties.filter((ip) => ip.target === target);
-  if (!tip || tip.length === 0) {
+  if (tip.length === 0) {
     return onProperties;
   }
 
@@ -93,11 +86,11 @@ export function propertyDescriptorPatch(api: _ZonePrivate, _global: any) {
       'HTMLMarqueeElement',
       'Worker',
     ]);
-    const ignoreErrorProperties = isIE()
-      ? [{target: internalWindow, ignoreProperties: ['error']}]
-      : [];
-    // in IE/Edge, onProp not exist in window object, but in WindowPrototype
-    // so we need to pass WindowPrototype to check onProp exist or not
+    const ignoreErrorProperties: IgnoreProperty[] = [];
+    // In older browsers like IE or Edge, event handler properties (e.g., `onclick`)
+    // may not be defined directly on the `window` object but on its prototype (`WindowPrototype`).
+    // To ensure complete coverage, we use the prototype when checking
+    // for and patching these properties.
     patchFilteredProperties(
       internalWindow,
       getOnEventNames(internalWindow),
@@ -118,8 +111,7 @@ export function propertyDescriptorPatch(api: _ZonePrivate, _global: any) {
   ]);
   for (let i = 0; i < patchTargets.length; i++) {
     const target = _global[patchTargets[i]];
-    target &&
-      target.prototype &&
+    target?.prototype &&
       patchFilteredProperties(
         target.prototype,
         getOnEventNames(target.prototype),
diff --git a/packages/zone.js/lib/common/utils.ts b/packages/zone.js/lib/common/utils.ts
index 5b3b82281e0..bf148e4f9aa 100644
--- a/packages/zone.js/lib/common/utils.ts
+++ b/packages/zone.js/lib/common/utils.ts
@@ -232,8 +232,10 @@ export function patchProperty(obj: any, prop: string, prototype?: any) {
   }
 
   desc.set = function (this: EventSource, newValue) {
-    // in some of windows's onproperty callback, this is undefined
-    // so we need to check it
+    // In some versions of Windows, the `this` context may be undefined
+    // in on-property callbacks.
+    // To handle this edge case, we check if `this` is falsy and
+    // fallback to `_global` if needed.
     let target = this;
     if (!target && obj === _global) {
       target = _global;
@@ -247,9 +249,10 @@ export function patchProperty(obj: any, prop: string, prototype?: any) {
       target.removeEventListener(eventName, wrapFn);
     }
 
-    // issue #978, when onload handler was added before loading zone.js
-    // we should remove it with originalDescSet
-    originalDescSet && originalDescSet.call(target, null);
+    // https://github.com/angular/zone.js/issues/978
+    // If an inline handler (like `onload`) was defined before zone.js was loaded,
+    // call the original descriptor's setter to clean it up.
+    originalDescSet?.call(target, null);
     (target as any)[eventNameSymbol] = newValue;
     if (typeof newValue === 'function') {
       target.addEventListener(eventName, wrapFn, false);
@@ -542,16 +545,6 @@ export function attachOriginToPatched(patched: Function, original: any) {
 let isDetectedIEOrEdge = false;
 let ieOrEdge = false;
 
-export function isIE() {
-  try {
-    const ua = internalWindow.navigator.userAgent;
-    if (ua.indexOf('MSIE ') !== -1 || ua.indexOf('Trident/') !== -1) {
-      return true;
-    }
-  } catch (error) {}
-  return false;
-}
-
 export function isIEOrEdge() {
   if (isDetectedIEOrEdge) {
     return ieOrEdge;
diff --git a/packages/zone.js/test/zone-spec/long-stack-trace-zone.spec.ts b/packages/zone.js/test/zone-spec/long-stack-trace-zone.spec.ts
index 9e1af7c5715..f35155b2825 100644
--- a/packages/zone.js/test/zone-spec/long-stack-trace-zone.spec.ts
+++ b/packages/zone.js/test/zone-spec/long-stack-trace-zone.spec.ts
@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import {isBrowser, isIE, zoneSymbol} from '../../lib/common/utils';
+import {isBrowser, zoneSymbol} from '../../lib/common/utils';
 import {ifEnvSupports, isSafari, isSupportSetErrorStack} from '../test-util';
 
 const defineProperty = (Object as any)[zoneSymbol('defineProperty')] || Object.defineProperty;
@@ -119,7 +119,7 @@ describe(
             div.dispatchEvent(enterEvent);
 
             expect(log.length).toBe(2);
-            if (!isSafari() && !isIE()) {
+            if (!isSafari()) {
               expect(log[0].stack === log[1].stack).toBe(false);
             }