Got https://barguide.com/games/zombie4/zombie4.html working on Waterfox Classic browser on my 64-bit Win8.1 laptop:
I had to install the latest Java 8 patch 261: “jdk-8u261-windows-x64”
But I believe more recent Java major versions should work too, as long as it’s the latest patch for it.
Once it’s installed properly, you’ll need to find Java on the “Windows Control Panel”.
Go to its “Security” tab and click at “Edit Site List…” like the screenshot from the link below:
Whitelist the zombie game site by adding this domain: https://barguide.com
On Waterfox classic browser, go to “Add-ons Manager” and check if “Java Deployment Toolkit” is there.
Make sure “Ask to Activate” option is enabled and you’re ready to visit the zombie link and have its Java applet load the game after we authorize some extra security popups.
Another great site to whitelist for lotsa Java applets is: https://www.greenfoot.org
We can run even its super old demo games:
https://www.Greenfoot.org/scenarios?sort_by=updated&page=2117