try just to headshot the zombies.saving much ammo. and if they r hunting u look for the next pine tree or bush and go in it. after they loose aggro u are good to go again ;)
maybe this guy here with the red eyes and a mountain dew in his hands :D front maybe: http://youtu.be/5UdXD7ZGobw?t=2m11s backside: http://youtu.be/5UdXD7ZGobw?t=3m6s