I dont know if its possible, but make it so that you control 2 players with the same controller, one controls the keyboard for player 1, and the mouse for player 2. Then vise versa for the other.
You guys should play one of the smallest maps in zombies history, call of duty ww2's groesten haus map, there is an easter egg to get to box and another one to always pull pack a punch weapons out of the box, I recommend a tutorial if you guys want to check it out!