First, a critical distinction. There is standalone Call of Duty: World at War Zombies app on the Google Play Store created by Activision. The official mobile port was released in 2010 for iOS and briefly for BlackBerry, but it was abandoned years ago and never officially updated for modern Android devices.
While you won't find it in a standard store, several community hubs host the necessary files: Reddit (r/CODZombies) : The primary source for the touchHLE APK and setup guides. Internet Archive call of duty world at war zombies apk for android
Activision officially shut down support for these older mobile titles around 2018 to focus on Call of Duty: Mobile . First, a critical distinction