Lane Zac is about owning blob space: trades are good when your spells drop blobs on a path you can walk, and bad when the opponent can stand between you and the sustain those spells are supposed to buy back
Start more top-lane trades with Q on a minion, ward, plant, or tower so the second hit creates the slam, then use short E to confirm or leave; that hand pattern is a lot cleaner than announcing every trade with a full-charge jump
Zac's best games are the ones where level 6 and a tank item let him keep people in contact through a second spell cycle, and the recent data fits that read: he is unusually fight-heavy for a top laner, soaking damage and joining kills more than he wins through isolated side-lane structure pressure
Use R when the fight is already close enough that each bounce keeps people in your space and gives you time to collect blobs, not when you are still trying to force first contact from too far out. In lane, that usually means after Q or short E has already made them commit movement. In skirmishes, press it once you know they have to keep walking through you, around terrain, or back toward their team. If you ult too early, they just disengage the first bounce and your health spend does not get paid back. If you ult on contact, the trade often keeps getting better for you.
Each time Zac hits an enemy with an ability, he sheds a chunk of himself that can be reabsorbed to restore Health. Upon taking fatal damage, Zac splits into 4 bloblets that attempt to recombine. If any bloblets remain, he will revive with an amount of Health depending on the Health of the surviving bloblets. Each bloblet has a percentage of Zac's maximum Health, Armor and Magic Resistance. This ability has a 5 minute cooldown.
Zac stretches an arm, grabbing an enemy. Attacking a different enemy will cause him to throw both targets towards each other.
Zac explodes outward towards nearby enemies, dealing a percentage of their maximum health as magic damage.
Zac attaches his arms to the ground and stretches back, launching himself forward.
Zac bounces four times, knocking up enemies hit and slowing them.