The Pokémon Company likes being random sometimes, and has released a Zoroark distribution for Pokémon Omega Ruby and Alpha Sapphire to prove that very point.
This particular version of the tricky 'mon comes with the Sludge Bomb move, which it can't learn in normal gameplay, with Dark Pulse, Flamethrower and Sucker Punch being its other options. It's available now as a Mystery Gift in North America, so players just need to hop online and do the usual honours in game to get it - the distribution ends on 20th November, though.
That's for North America, while in the UK it'll be distributed as a serial code in GAME stores from 6th November to 26th November - thanks, Serebii. Supposedly the code will also be redeemable in X & Y in the UK, despite indications being that it's ORAS-only in North America.
In any case, let us know whether you've picked up your free Zoroark in North America; it's a tricky little 'mon and worth adding to your team.