I recommend that you keep Extrasensory. Zoroark's special attack is a bit higher than its regular attack. However, if you want a reliable coverage move that never misses, Aerial Ace is a good move. Here's a recommended moveset for a mixed Zoroark:
Zoroark@Life Orb/Focus Sash
Ability: Illusion
Nature: Naive
EVs: 252 Speed, 126 Attack, 126 Special Attack
Moveset:
Dark Pulse/Night Daze (Your STAB. Dark Pulse is an egg move, or can be learned with TM 97. Either go for raw power with Night Daze, or go for slightly less power but a flinch chance with Dark Pulse.)
U-Turn (Your coverage move. Can hit any type and will help you scout. Zoroark is very fast, so it can stay on board and switch in/out while confusing the foe with its Illusion ability)
Extrasensory/Flamethrower (Another coverage move. This one is a lot like Dark Pulse, not too powerful, but has a handy flinch chance. Helps cover it's Fighting type weakness. But Flamethrower can also be useful if you need to fry those pesky steel types.)
Aerial Ace (Your last coverage move. This move will never miss, and hits two of its weaknesses, Bug and Fighting.)
