Here is the full list of all 23 Zombie Desperation achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Unlock the First 8 Files
Unlock 1 file
Kill 50 Zombies With The Flamethrower
Pick Up an Ammo Crate
Unlock The 'Offices' Level
Use a Rocket Launcher
Unlock The 'Hallway' Level
Kill 50 Zombies With The Grenade Launcher
Unlock The 'Power Room' Level
Kill 1000 Zombies
Unlock The 'Prison' Level
See the Game Over Screen for the First Time
Kill 200 Zombies
Survive For 10 Minutes
Kill 50 Zombies With The Shotgun
Kill 50 Zombies With The Rifle
Kill 10 Vermins
Kill a Bleeder
Kill 10 Bleeders
Kill 30 Vermins
Kill 30 Bleeders
Kill 50 Zombies
Unlock The 'Entrance' Level