Zac's Skill Max Order: W → E → Q
Level 1: Quinn Cheese level 1, and then punish Zac with your AA-E-AA combo. He can't do anything level 1, so run him down.
Level 2: Level 2 onwards, save E to cancel Zac's Jump. You can E him mid air, and you will cancel his leap and be pushed back to safety. Save E level 2 onwards to cancel this ability.
Level 3-5: Zac can't do much in lane, just save E to counter his engage, and then melt him with autos for the rest of the lane.
Level 6+: Zac's R can only knock you back once, so when he uses R, let it knock you back once, and then E after the knock back. If you E too early, his R will cancel your E.
Early game play aggro, and save E to cancel his E jump.
If you only use E to cancel his E, then he is useless and can't do anything in laning phase.
Use your range advantage to bully him, and scale up your tank shred items to stomp him later on in the matchup.
Step on blobs to prevent his healing whenever you can.
Ignite early during an all-in to prevent his blob healing.