It is possible to 1 cycle Zant in both phase 1 and phase 2. The idea behind this is to interuppt Zant disappearing and hence being able to kill him in 1 cycle. To do this mash 3 jump-attacks and then time the 4th jump attack with slight delay, If you mash all jump attacks then he will just disappear for a normal 2 cycle, If you time every jump attack then he dodges too early and you can't kill him. Once you time the 4th jump attack correctly and he dodges you then do 2 more jump attacks to finish him off.
As soon as you start the fight c-up and and throw the boomerang and slightly above you where Zant will spawn, this knocks him down immediately. Start your combo as he hops along so the 4th hit damages him. Repeat this once more to progress
Just like Phase 1 it is possible to 1 cycle this phase although it is slightly different and has a two frame window.
Start with a Jumpslash into a qucikspin, stab Zant twice, half charge a quickspin to delay the third slash and then finish the combo.
Zant be in the wrong place 2-4 times which is completely random. As soon as the fight starts mash boomerang while you fall, this will make the first 2 cycles disappear and if you got he best RNG he will start attacking for the first time where you just combo him again. The second time round you target and use boomerang to quickly dispatch of the fake Zants and then finish him off again with a combo.
It is possible to only use 2 water bombs for air refills if spaced out correctly. When starting the fight equip Iron boots and L+A roll twice to get as close as possible to the Zant head. Clawshot Zant as the mouth opens and then refill your air meter with the first water bomb, make sure you go away from the zant head when doing these otherwise he could blow air and knock the bomb out of your hand causing you to drown.
Now using Iron Boots go and stand at the opposite side of one of the Zant Heads appearing. When you can fully see the eye of the Zant Head appear from the ground the game has determained Zant will be in the one furthest away from you, it is also at this point you refill your air for the last time with your 2nd water bomb.
Using Iron Boots Swim over to Zant avoiding his shots and clawshot and combo him to finish him off and move onto the next phase. The first air refill is tight on time so if you want to be safer refill your air before clawshotting him the first time and make it a 3 bomb.
It is slightly faster to do the combo of "right, left, up, down" than the usual "up,up,up,down". This gives you a little more time to refill your air if you don't have the zora armour
The position of Zant is decided when the heads stop moving up, if you time swimming over to his location right you can clawshot him as he is revealed and hence he won't has a chance to attack
Equip B&C Over Boots and roll towards the pillar Zant is going to and roll into it twice, then combo him for the first cycle. Now roll to the middle pillar and swing the ball & chain around your head, this will knock down Zant as soon as he spawns. Combo to finish the phase.
It is slightly faster to do a "Jump Attack, then a fast combo of (right,left,up,down)" on the first hit then the 2nd hit do a "Jump Attack into Spin Attack" as opposed to traditional "up,up,up,down" combo for both hits. You can pull sword out faster by pressing B to put away B&C while holding B&C button.
There are plenty of hearts in the pots while waiting for Zant to come down. Wait near the wall as Zant cannot stomp on you next to the wall, now use the Ball & Chain on his foot and stay close to him with your sword ready. You can start your combo once he is half-way deflated. Rinse and Repeat for second cycle.
Hold L+UP before the phase starts and when the right pillar falls mash B to hit him with the 4th hit (combo), he can't be hit with any other stabs before that. Now start a combo in any direction but up (where Zant will spawn) and target Zant to him with the 4th hit again. Now turn around and spin-attack to stun him and start the combo facing away from Zant and target him to hit him with the 4th hit for the final time