Keep an eye on Humble Bundle or Fanatical , where the trilogy is often bundled with other games for just a few dollars. System Requirements (PC)
Are you planning to play through the , or are you looking to set up a co-op session with friends? Zombie Army Trilogy on Steam zombie-army-trilogy-free-download
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) Keep an eye on Humble Bundle or Fanatical