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