I was wondering, since the first part of mirror forces effect is to stop the attack, can I use tutan to stop it whtn activated on my zombies.

Mirror Force doesnt designate (or "target") anything. Whatever is on your side of the field in Attack Position is destroyed, as well as it must be an effect that only targets "1" monster, so it doesnt matter if you only have Zombies on your side of the field. Mirror Force doesnt care what's there, only that its in Attack.

In all fairness, maybe he just has a Mirror Force with the old text on it that says "negate the attack . . ."

However, what woo says is truth and is how the scenario should be played out.