To be honest, the zombies should actually have an upper hand in the game. Hence, "Zombie Survival". I've had this type of experience before, without the suicide. If anything you can just make them waste all their bullets on you, and have them use up more points. This actually helps motivate a lot of us in the zombie team to keep attacking and win the round. Have them stack up, and go in all at once then. That's my perspective of it.