I never figured out how to get it so when a (just say a zealot) zealot comes to attack an idle unit (that will NOT attack back), it won't switch to a different unit that is attacking it. Like is Resident Evil: Racoon City, the zealots come and there are barriers of tanks around and our guys are behind attacking the zombies, the zombies attack the tanks enstead of our guys that are attacking them.
Note: I want the zealots to be attacking the guys that are attacking them after the tanks are out of the way.
Set the Alliance Status of the units that are attacking to Enemy with who they're attacking, and set the Alliance Status of the units being attacked (but not attacking back) to Allies with who they're being attacked by.
Raccoon city's triggers are just "Patrol to location", the tanks are owned by player 12, perhaps the AI just automatically attacks p12. Thats all that I can think of anyway, as there doesn't appear to be a trigger telling the zombies to do anything other than patrol to the middle of the map.
I replaced attack with patrol and it works! Thanks lots.

I request this topic to be close whenever you see this message. I got my question answered.