I need one desperately. I’m playing Trevenant BREAK, which has Weakness to the Pokémon in about 99.9% of all Expanded decks. Unfortunately, I can’t think of any. Regionals is only in a couple of days... HELP PLEEEEAAAASE!
I try to play the most consistent list I can, but I lack Rescue Scarf.Weakness policy is always a thing, though probably not the best choice. Maybe an Espeon EX to get rid of any Zoroarks that have taken two attacks from Trevenant BREAK? You'll only get one prize card for each one you get rid of, but it will get rid of them nonetheless.
Other than that all I can think of is the obvious answer: consistency. Just build a list consistent enough to be able to easily lock down a Zoroark Player. Unless I'm mistaken, Zoroark if often used in the speed decks a lot, and those decks play a lot of items, so Trevenant should hit those decks hard anyways (I assume you use the XY normal Trevenant).
I'm not going to the regionals, don't do much competitive stuff, and overall and probably not qualified to give you advice. I just thought I'd try and help, but keep in mind I could be wrong.