there is a glich in the zombie mode all you have to do is in the begining walk to either one of the walls and crouch (duck) and the zombies will stop above you and the ones from the other end will keep coming towards you just shoot them BUT DONT STAND UP THE ONES ABOVE YOU CAN ATTACK YOU IF YOU do. i was able you get 777 kills this way then i let go ogf the duck butten and got killed press + if this helped