Thankfully, the Zoroark you encounter is female, so you can breed it with something. How about you transfer something over that knows Dark Pulse, like Lucario, and breed it with Zoroark?
I haven't done the Tornadus event, but I know that I'll be spending an eternity trying to get one with good IVs/nature.
Cool, I'm playing Black, too. Who's in your team?