Here is the full list of all 68 Zombie Army Trilogy achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Kill 25 Fire Demons
Reach Wave 10 in Horde Mode – Dead Man's Bluff
Reach at least Wave 10 in Horde Mode – Cathedral
Reach at least Wave 10 in Horde Mode – Flood of Tears
Reach at least Wave 10 with the highest score in any Horde Mode map
Reach at least Wave 10 with more gold medals than your companions
Reach Wave 10 in Horde Mode – Dead End
Reach at least Wave 10 in Horde Mode – Waves of Despair
Complete every Survivor sidequest
Collect every Gold Bar
Loot a Super Elite's corpse
Successfully complete all Chapters on Sniper Elite difficulty
Kill 5,000 enemies of any kind
Find and shoot every Bottle of Blood
Put the tortured souls in the Forest out of their misery
Reach a total shot distance of 50km
Loot a Chainsaw Elite's corpse
Save the man in the hospital
Become possessed
Successfully complete Tower of Hellfire
Kill 50 Super Elites
Successfully complete Terminal
Kill 25 Summoners
Successfully complete Crucible of Evil
Pick up a phone
Kill 100 Zombie Snipers
Successfully complete Gateway to Hell
Successfully complete Purgatory
Get an unbroken 10-headshot streak
Successfully complete Subway to Hell
Successfully complete Library of Evil
Kill 500 Skeletons
Revive other players 50 times
Kill an Occult General
Kill 50 enemies that are actively attacking other players
Successfully complete Labyrinth of Death
Kill 20 Elites in co-op
Kill a Suicide Zombie by hitting his grenade
Successfully complete Cathedral of Resurrection
Complete any Campaign chapter in 4-player co-op at any difficulty level
Get at least 20 for 1 with an explosive kill
Kill 50 Suicide Zombies
Reach a Chain Count of 30
Successfully complete Village of the Dead
Defeat 500 enemies with headshots
Successfully complete Army of Darkness
Sever 1,000 limbs
Headshot a Heavy Armour Zombie without removing his helmet
Reach a Chain Count of 20
Pick up a Panzerfaust
Successfully complete The Keep
Kill 20 enemies as they revive
Successfully complete Forest of Corpses
Kill a total of 20 enemies while incapacitated
Successfully complete Freight Train of Fear
Kill a Zombie Sniper in mid-air
Kick 50 enemies down
Pick up the Preacher
Get at least 10 for 1 with an explosive kill
Get at least 15 for 1 with an explosive kill
Successfully complete City of Ashes
Reach a Chain Count of 10
Kill a Survivor
Get a 5-for-1 kill with any sniper rifle
Sever 10,000 limbs
Score 5,000 with a single sniper round
Shoot the 3 Zombie Ravens outside the Folterschloss
Complete levels as every playable character