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