If an opponent gains control of Zidane and one or more other permanents from you simultaneously, Zidane's last ability will trigger for each of those permanents, including itself
However, if you do choose a target, and that target is illegal at the time Rat Out tries to resolve, the spell won't resolve and none of its effects will happen
Ral Zarek is solid for your decks, and I played him in my Standard deck that did some damage at FNMs at the time, as people would really respect Ral in that era, especially with the Double Lightning Bolt available for four mana at -2
You need creatures and at least 1 basic land for it to function
It also requires efficient and effective pregame conversations, as without them the power levels dont mean much