Unfortuneately we only had like four zombies. Because of this, giving them a little "Dawn of the Dead Syndrome" is fine. There were zombies hiding around corners or just inside of doors waiting for teams to come inside. That's a little more intelligent then I would give the normal zombie but you can't fault them entirely - the poor guys are horribly outnumbered, unarmed and constantly being lit up by players.
I say: let it go. I have.