What are some alternatives?
When comparing Zandronum and Quake, you can also consider the following products
Doom - Doom is a science fiction horror-themed first-person shooter video game in which players assume the...
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
AssaultCube - AssaultCube is a FREE multiplayer first-person shooter game. Taking place in realistic environments, with fast, arcade gameplay, it's addictive and fun!
Overwatch - Stylized team-based FPS
Black Desert Online - This Korean developed MMORPG offers a dynamic, action-based combat system in a richly developed fantasy setting.
Unreal Tournament - Unreal is a series of first-person shooter video games developed by Epic Games.