Here is the full list of all 39 ZomDay achievements.
Head shot count over 200 at a single wave
Finish the training level
Donate 1000K to the donate machine
Life counts reach 9
Open 50 AirDrop boxes
Kill any kinds of Boss monster for 10 times
Finish the 'Battle of Slum' level in 'god of war' mode
Finish the 'Abandoned Factory' level in 'god of war' mode
Finish the 'Bloody Desert' level in 'god of war' mode
Finish the 'Sniper in the slum' level
Finish the 'Sniper in the slum Ⅱ' level
Get the SSS Rank
Get the Omega Rank
Reaches $88888 when level's final wave completion window shows up
Combo count reaches 200
100% hit rate at a single wave
Recieve 20K damage in a single wave
Kill 10K enermy
Health reaches 10K
Collect 200 purple coin
Finish the level 'Wild-West'
Finish the level 'Battle of Slum' in normal mode
Finish the level 'Battle of slum' in hard mode
Finish the level 'Battle of Slum' in hell mode
Finish the level ‘Abandoned Factory’ in normal mode
Finish the level 'Abandoned Factory' in hard mode
Finish the level 'Abandoned Factory' in hell mode
Finish the level 'Bloody Desert' in normal mode
Finish the level 'Bloody Desert' in hard mode
Finish the level 'Bloody Desert' in hell mode
Finish the level 'Team Zeta' in normal mode
Finish the level 'Team Zeta' in hard mode
Finish the level 'Team Zeta' in hell mode
Finish the level 'Team Zeta' in 'god of war' mode
Finish the level 'Disturbia'
Finish the level 'DeepDarkHole' in normal mode
Finish the level 'DeepDarkHole' in hard mode
Finish the level 'DeepDarkHole' in hell mode
Finish the level 'DeepDarkHole' in 'god of war' mode