Zac is a champion most players would associate with the jungle role and nothing more but he can be played with success as a top laner or even a support (at least in Gold/lower elos). Zac brings a unique playstyle to toplane that usually involves near-endless harassment of the enemy champion, high sustain even without items, and an E ability that makes it almost impossible to successfully gank him. Whereas in botlane he is an all-in engage champion who's goal is to pop the enemy adc faster than they can respond with his double knockup and Q displacement.

Zac excels in displacement, Sustain, Crowd Control, and Mobility. He his easily the most mobile tank in the entire game and among the most mobile champs in the game period who is capable of dealing significant damage even as a full-tank with an undying passive to boot. Zac doesn't rely on mana either, making him an ideal pick against very mana hungry champions that Zac can outlast in lane and pick fights with when they don't have enough mana to respond!

Zac is not without his weaknesses though! he is very vulnerable to ranged harass, grievous wounds, %hp damage effects, and his E has a charge time which gives enemies time to interrupt your jump and leave you a sitting duck for a significant amount of time at least in the early-game.

Zac in the toplane is a high sustain bruiser that many opposing champions will have zero kill pressure against between his E disengage, and his undying passive

You typically want to pick Zac into Meelee champions and/or champions that have mana issues early as you want to be bullying with W early as the enemy tries to farm, and when you put a few points in E to get it's cooldown to a more reasonable amount you can start going for burst trades and even kills. But be cautious, Zac is very vulnerable if you overextend without your E

Against difficult ranged matchups or an enemy champion that you are unable to trade with or outsustain you need to play very passive and just keep your hp up by W'ing minions and picking up your goo. Zacs W has no cost, but still drops globs of goo from his passive Cell Division that will restore a % of your maximum health when collected so it's your bread and butter for keeping your hp pool topped off.

Lategame you can function as both a very safe splitpusher by leaving your E up to get the hell out when the enemy comes to stop you, or a potent engage tank for teamfights that can dive the backline and wreak all sorts of havoc on the carries.

Teleport and Flash is the only summoner spell combo I would take if you're bringing Zac to the toplane, you just don't have the early kill pressure to make ignite worth taking and teleport allows you to do help your other lanes out across the map as well as maintain pressure on your own lane and avoid missing cs. Teleport is also extremely useful for splitpushing strategies and backdoor opportunities!

Support Zac is a bursty tank with one goal and one goal only - Jump on the enemy adc and burst/displace/cc them for as long as you can while your own adc wails on their face. Support Zac is a very different playstyle to toplane and jungle Zac that have a very heavy focus on sustain whereas support Zac is all about taking advantage of Zacs crowd control and burst damage potential.

Zac support combos well with high burst adc's like Draven, Lucian, Jhin, Miss Fortune and if you're in the mood for some spice Bot ADC Yasuo. These adc's can best take advantage of the damage window you provide during your E W Q R engage to hopefully make short work of the enemy carry over and over again.

Zac support struggles against anti-engage supports like Rakan, Lulu, Thresh, Morgana, ranged harass supports like Brand, Viegar, and Vel'Koz, and high poke/high mobility ADC's like Ezreal, Caitlyn, Lucian, Vayne, and Kalista

Against an easy/immobile lane matchup I would take Ignite/Flash to add even more damage to your burst and allow you to win lane that much harder

Against a difficult lane matchup, Exhaust/Flash or possibly Barrier/Flash should be taken to allow for a safe playstyle while you wait for your adc to farm and your jungler to gank.

Your towers are your best friend: If your passive is up and you're near death but your lane opponent is just too strong to finish off don't hesitate to use your E and Flash to beeline towards your tower before you die. Most champions especially early won't be able to take out all 4 of your globs while under your tower!!!! Use your abilities to force opponents to take tower shots if they get too close with a bami's cinder or while you are ignited!

Q control: Zacs Q has a lot of utility and with practice you can start to identify moments where you can control fights with Q. You can Q an assassin jumping on your carry, and auto an enemy closer to you to peel the assassin off your adc, you can Q a fleeing enemy and a minion to pull the enemy back towards your team, if your lane opponent has sunfire or bami's cinder and are under your tower you can E on top of them to get damaged by their bamis and trigger tower aggro on them, and then Q the opponent and auto a minion to keep your opponent in range of the tower for a bit so they take a couple free tower hits.

E plays: By maxing E first the range becomes absurd and lets you perform engages and roams from all these ridiculous angles and locations that the enemy won't be able to predict. Good spots are are either sides chicken camp (both in the camp itself, and in that rounded wall that faces the nexus on either side), Red buff pits on either side (You can reach baron/dragon pit from the red camps with maxed E, and many more.

R combos: One of the most important and sneaky tricks Zac can do post-6 is an under-tower lockdown with his E+R combo (this works best vs melee opponents). When your opponent is autoing your tower, wait till they only have 1-2 minions left and fly in from outside their vision with E and immediately R+W to kill the remaining minions and force your tower to aggro the enemy champion while they are double knocked up towards the tower. This almost always guarantees either a kill, burned summoners, burned ultimates (tryndamere), or sometimes even all of the above. This is a similar concept to the toplane skarner ult stun combo.