- Estimated difficulty: 5/10 (in co-op) 7-8 (solo).
- Offline: 56 
- Online: 12  are online required but all 68/68 (1,000) can be done in online co-op games.
- Minimum time to 1000: 25-45hrs
- Minimum playthroughs needed: 1, 2 recommended - Cadet & Sniper Elite difficulties.
- Difficulty affects achievements: Yes, Sniper Elite difficulty required.
- Missable achievements: None
- Glitchy achievements: 1 (gold bar not showing).
- Unobtainable achievements: See Roadmap.
- Extra equipment needed: No
Currently the game only has 67/68 970/1000 available due to a glitch with a gold bar on Crucible of Evil, a patch has been announced for 'early April' so this should be obtainable soon.
Zombie Army Trilogy is a 3rd person Zombie Horde survival game, made in the same engine as Sniper Elite 3 remade in part from the original Nazi Zombie Army games made from the Sniper Elite V2 game. It includes the death cams in the sniper elite games, and various sniper rifles. The main differences are the chains of explosions and heavy requirement to use your explosives when faced with massive waves of zombies, coupled with some harder elite style zombies with various weaknesses and strengths.
Anyone familiar with the Sniper Elite series will likely already know this, but for those who don't progress on things such as severed limbs, collectibles or monster kills are saved automatically, so if you want to farm a specific spot for monster kills on demons, snipers or whatever you can kill them then reload checkpoint and kill again repeatedly if you wish.
Part 1 - Campaign Run:
First you want to lower the difficulty down to Cadet as playing in Marksman offers no achievements at all. In Cadet the bullets go on the cross hair making blood bottles and accurate shooting easier. You can play in a private game with a friend if you like, up to you if you want to lower the enemy spawn to one player to speed through quicker. The campaign has three chapters and five missions in each chapter.
Each mission has five gold bars and four bottles in the game, you will want to collect these on this playthrough to save time. For a collectibles guide go here https://www.youtube.com/playlist?lis...nqHvmvfMJg6k2E
Now start your campaign and get used to the game, explosives are the best method for taking out large hordes of zombies / skeletons. If you find yourself in a bad situation throw a grenade or two and watch the body parts fly! Along this playthrough you should net yourself a vast majority of the solo-able achievements (44/68). Some achievements like the 10 unbroken head shots and the explosive related achievements may may require an easier mop-up method afterwards.
So after you finish all the campaign go back and finish up any of the solo achievements you couldn't finish previously, you can set up private games with four player spawns on labyrinth of death if you missed the 20 explosive kills, chain count 30, five in one kill, or 5,000 score with one bullet achievements.
The kill XX Super Elites, Zombie Snipers and Summoners will be gained once you do the co-op campaign run, but you may need to farm Fire Demon kills as there aren't many Fire Demons in the game.
Part 2 - Online Horde Mode:
The online to this game isn't very good honestly, if the host leaves the game ends. Being the host is nearly a necessity but you cannot host a public game unless you try join an online game with nobody playing and get made host, I'd recommend trying to find at least one friend for the horde mode. Now all you need to do for these achievements is reach wave 10, make a private game or get lucky making a lobby, set the difficulty to cadet and enemy spawns to one player, with a friend it shouldn't be hard to reach wave 10, even with a few randoms it can be very easy.
During the online horde mode make sure to revive fallen allies, take out zombies with your pistol if you fall down, protect allies being hit by zombies and attack any Super Elites that spawn, these will all count toward achievements also try be top scorer on a horde map and receive the most medals. If you work with a team of friends or one friend if you host you can get your friend/s to leave and re-join after a few waves so you will always be the top spot. You'll also get five more achievements for getting to Wave 10 on each map.
Part 3 - Sniper Elite Campaign Completion:
This will be the hardest part to complete, by now you should most likely have 66/68 achievements or close to it, the only missing ones being this, "Leave the limbs you've lost" and possibly some of the Kill XX special enemy achievements, if you didn't farm those.
Easiest way to complete the game on Sniper Elite difficulty is in online co-op, you can do it solo but it's incredibly difficult at times. Luckily you can do it with friends, seek fellow achievement hunters or play public games with varying luck on being host. Set the game to Sniper Elite difficulty, one player spawns this will cause only one players worth of enemies to spawn for you. Then try to have a minimum of three players total, as this makes it very easy, most missions can be done with two players, but three is much smoother and four is even better.
The main difference in Sniper Elite difficulty is you take insane damage, the bullets do travel on the cursor (like in Cadet) but your scope wobbles more, the most dangerous thing in this run is the Super Elite's with heavy machine guns, don't get close or you'll die in a second, keep your distance use cover and head shot him as much as possible.
Suicide Zombie's can also one shot you in this if you haven't got full hp and take an almost direct explosion, be much more careful with your own explosives too as these also can kill you very easily. I'd advise taking a shotgun and switching to if one of these guys gets too close, a shot toward the face should drop him to the floor.
Snipers tend to take 2-3 shots to take you down but they jump almost immediately after firing and take multiple shots to kill, its best to focus these guys down first (if no suicide zombies are coming) in a smaller group (2-3 players) as losing a player mid-fight before the zombies have even arrived can cause a lot of problems.
Part 4 - Mop Up:
After finally beating Hitler on Sniper Elite difficulty co-op, you may be missing a few achievements still, such as the kill XX amount of this type of creature or severe 10,000 limbs. Progress carries over through different playthroughs online or offline so you can work on them gradually or if you want them out the way early you can use chapter select find a level with the creature you want kill it and reload checkpoints to farm them.
Most of the achievements will come naturally as you progress, some require a bit of grinding and some will take a bit of preparation or some help from friends/fellow achievement hunters but overall you shouldn't struggle too much following these steps. Enjoy your 100% completion!
[XBA would like to thank SharinganAJ for this Roadmap]