It’s often compared to Left 4 Dead or Call of Duty Zombies but with the signature "X-Ray Kill Cam" from the Sniper Elite series.
Platforms like the Epic Games Store or GOG.com occasionally offer "free-to-keep" weeks for older titles. zombie-army-trilogy-free-download
If you enjoy the trilogy and want more, you might also look into the sequel, Zombie Army 4: Dead War , which features improved graphics and more weapon customization. It’s often compared to Left 4 Dead or
It takes about 13.5 hours to finish the main story and up to 34 hours for completionists. How to Get it Safely (and Free/Cheap) Zombie Army 4: Dead War