In order for you to play Zombie Panic! Source on Linux with minimal graphics settings, your computer must meet the following requirements
Operating System:
Latest Ubuntu LTS or higher
Processor (CPU):
2.4 GHz Dual Core Processor or better
Memory (RAM):
2 GB RAM
Graphics Card:
OpenGL compatible with Shader Model 2
Network:
Broadband Internet connection
Storage:
8 GB available space
Sound Card:
Compatible with PulseAudio