You will encounter many locked collectibles as you progress through Zombie Army 4‘s nine levels. Some are obtained by completing missions/objectives, while others require solving puzzles.
There are three puzzles in the nine levels of the game. Once you complete the puzzle, you will get rewards locked in the safe. This guide briefs out the solution of each puzzle in Zombie Army 4.
Gas Rats Puzzle
In the War Machine chapter, enter the safe room with a “Gas Rat” message written on the wall with five gas masks hanging. This is your cue to hunt five rats wearing masks. Exit the safe room, and the first rat will be sitting on the missile in the middle.
To find the next rat, go through the door the Butcher breaks and go around to where the Upgrade Kit is. Look at the pipe on the left wall. The second rat is on the pipe.
The third rat will be found after you enter the deep water. Once out of it, head left, where you will find a pile of pipes. The rat will be on these pipes.
To find the fourth rat, stand near the sealed door and look left of the door towards the machinery. Look for a red flashing light. The rat is hidden behind the machinery and is back towards the wall.
The last rat will be outside the safe room near some crates.
After all the rats are killed, you can access the safe. As a reward, you will receive divine grenades and a divine attachment.
Stranger Things Lights Puzzle
Near the end of Death Canal Level in ‘The Shadows of Venice Lights’ chapter, you will be met with another puzzle to help unlock a secret safe. Once you enter the puzzle room, you will see “Use your Brains” written all across the left wall.
Go past the bookshelf into the other corner of the room and shoot at the lights in an order spelling out BRAINS. Once you shoot the bulbs in order, the safe will open.
Inside the safe, you will find an artillery flare.
Pull the Lever Puzzle
In mission 8, Obliterate Hitler’s Army, you must turn on a series of levers. The first one is near the corner of the workshop at the beginning.
For the second one, turn back and move toward the workshop and you will find the next lever near the workbench.
Once both levers are pulled, interact with the generator to power it up. This will unlock a safe containing Divine MG between the crates. Pull one last lever before escaping the sewers to get Divine Attachment for your weapon. You will find this lever on the upper level, led by ladders.
