As I understood it, yes, his tanks my stand a chance at being “killed” by the zombies. However, they would remain casualties and take a shot at the plane. Yes, zombies can’t kill the plane; but the tank casualties can.
Plus, add in the fact that there is a 1/6 chance for zombies to kill a defender and a 1/3 chance for them to kill attacking ground units.
Plus, remember to remove any killed zombies during EVERY roll. I was in the AAZ tournament too and we forgot to remove killed zombies a LOT during our rolls.