It can only be obtained by either evolving a Zorua, though it could once be obtained through an event by transferring either a Shiny Entei, Suicune, or Raikou. By bringing the legendary with you in your party, you can initiate a event where you get to face a girl in a trailer located in Lostlorn Forest, who has what seems to be one of the three Legendary Beasts. Attacking it, however, reveals that its actually a Zoroark, and can be captured. When caught, it will know the moves Fury Swipes, Faint Attack, Scary Face, and Taunt.
Zoroark appears in a new Pokémon movie called Zoroark: Master of Illusions. In that movie, Zorua called Zoroark "Meema" (Pronounced Mi-Mah) throughout. It may be Zorua's way of calling Zoroark his mom.
Zoroark is likely based on the Kitsune of Japanese folklore, a shape-shifting, mythical fox that would trick unsuspecting travelers for fun. This is similar to Ninetales, another Pokémon based on the Kitsune. Zoroark also resembles a Werewolf, a mythological beast that was human but could shape-shift into a wolf or an anthropomorphic wolf-like beast.
Zoroark's name comes from zorro, which is Spanish for "fox", and "dark".
Zoroark in the first non-legendary Pokémon to be completely event exclusive and unobtainable during normal game play.
Zoroark is the first Unova Pokémon ever seen in the anime. (Zoroark: Master of Illusions)
Zoroark is said to be on the list of newcomers for the new Super Smash Bros. game.
In Black 2/White 2, a Backpacker that talks to you about Zoroark and a new TM you received. The hiker is later reveled to be a Zoroark under disguise of a Backpacker, then you notice it escaped.
Despite getting N`s Zorua from the house in Driftveil City in Pokemon Black 2/White 2, N still appears to have a Zoroark, which leads you to N`s Castle. Although it has been confirmed that N had three different Pokémon as a child, one being a Zorua, he could have had another one which wasn't seen or captured or otherwise obtained another Zorua at a later date.