Enter first person, aim the camera slightly upward, and hesitate for about a second before throwing the Boomerang. If timed well, it will knock Zant down. Time beginning a sword combo so that its 4th part will hit Zant as soon as he lands and becomes vulnerable. (The other parts of the combo don't need to hit Zant at all.) This can be tricky to time, as the amount of time Zant spends hopping is RNG. Aside from targeting Zant to throw the Boomerang, cycle 2 is identical to cycle 1.
Greatspin can be substituted for the 4th part of the combo if available, which makes timing the attacks easier but does not save any time over well-timed combos.
Knock Zant down with the Boomerang. Once he lands, chain 3 jump attacks, hesitate, then chain 3 more jump attacks. The 4th of the 6 jump attacks must be timed to hit Zant just as he's warping away; if successful, Zant will not take a hit, but he will move slightly and not warp away, and the controller will still vibrate.
The amount of time this saves over the 2-cycle described below varies, as the amount of time Zant spends hopping on the water after being knocked down in each cycle is RNG. Given good RNG in either case, the 1-cycle saves a very small amount of time over the 2-cycle and is uncommon in RTA runs.
Run into Zant's attack to begin invincibility frames, then immediately jump attack + quickspin. Hit Zant with the first 2 parts of a sword combo, then hold B to delay the 3rd part. Time releasing B for the 3rd part, then finish the combo. The 3rd part of the combo must be released within a 2-frame window for the 1-cycle to succeed. If Zant warps away without the 3rd part landing a blow, then it was released too late; if Zant takes hits from the entire combo but the fight does not end, then it was released too early.
On each cycle, Zant will spawn 2-4 times invincibly (laughing and jumping) before spawning to shoot his attack. Throw the Boomerang while falling as the fight begins to clear at least one of Zant's invincible spawn locations. Target and throw the Boomerang or approach Zant to clear the remaining invincible spawns, then complete a full sword combo once Zant spawns vulnerably. Repeat for cycle 2.
It is recommended that beginners save the game before using bombs in this phase, as the nearest backup water bombs are in City in the Sky. Anyone uncomfortable with this phase may consider opening that water bomb chest while already in City in the Sky earlier in a run.
In cycle 1, equip Iron Boots and target roll (L+A) twice to be close to the Zant head without being so close that the nose bubbles will hit Link. Aim the Clawshot slightly higher than horizontal, and shoot it to clawshot Zant as soon as the mouth opens. Perform a sword combo with the control stick held right, left, up, then down for the four parts; this combo is fast and will make the air refill timing less tight. (Beginners can also choose to use a third bomb for a refill at the very beginning of the phase to make this refill far less tight.)
As soon as possible, swim with a water bomb to refill the air meter. The window for this refill is not long, but be careful not to rush dropping the bomb and rocket Link to the ceiling, forcing him to drown. Leaving the control stick neutral or swimming away from the Zant head during the air refill will work, but swimming towards the Zant head may result in the nose bubbles knocking the water bomb out of Link's hands, preventing the air refill.
In cycle 2, stand on one side of the arena's central crater and wait for the four Zant heads to begin to rise. Zant will always spawn in the head farthest from Link, so begin swimming with a water bomb across the diameter of the crater as soon as the full eyes of the Zant heads are above ground. Drop the water bomb for an air refill and use the Iron Boots to tap swim and land near Zant. Wait for him to finish his attack, clawshot him, and perform the same sword combo as before to finish the phase.
This video demonstrates that the right, left, up, down combo is faster than an up, up, up, down combo.
The fight with Zora Armor is only slightly different from the fight without Zora Armor:
Do not use bombs to refill the non-existent air meter.
For cycle 2, it is possible to time swimming across the crater and landing on the other side to clawshot Zant before he shoots his attack, saving a few seconds.
If Mortal Draw is available, mash A to mortal draw Zant after clawshotting him in cycle 1. Then, in cycle 2, one stab will finish the phase.
Equip Ball & Chain over Iron Boots and roll towards the pillar that Zant is hopping to, which is always the same pillar. Bonk into the pillar twice to knock Zant down. Jump attack (no spin) and then complete a 4-part combo (ideally right, left, up, down) to end the cycle.
Quickly roll to the center pillar and twirl the Ball & Chain to hit the pillar 2 or more times and knock Zant down. Press B while still holding the Ball & Chain button to pull out the sword quickly. Once Zant lands, jump attack + quickspin to finish the phase.
If Greatspin is available: Greatspin once for cycle 1, then stab once for cycle 2.
Wait by any wall so that Zant's feet will not hit Link when he falls, and break pots for health if desired. As soon as Zant begins to fall, press the Ball & Chain button to throw it and hit his foot as soon as it is vulnerable. Take out the sword and stay close to Zant as he hops. Once he becomes vulnerable after several hops, complete a combo on him. Repeat all steps for cycle 2.
Just as in the other phases, Zant only needs to be hit by the 4th part of a combo to finish a cycle. However, because he stops moving when hit, it is much easier to begin a combo when he becomes vulnerable than to pre-empt his vulnerability like in Phase 1 (Diababa). If Zant is too far away to hit at any point while vulnerable, a jump attack can help catch up to him.
If Greatspin is available: Greatspin Zant once when he becomes vulnerable on each cycle.
As the fight begins, hold L and up on the control stick. As soon as the right fencepost falls, start pressing B repeatedly; this will time the first 3 parts of the combo to miss Zant, but the 4th part to hit.
Start a combo facing backwards (towards the camera), then target Zant and hold up on the 4th part of the combo to hit him.
Hold B to charge a spin attack, hesitate for about half a second, and release the spin attack to counter Zant's spin attack. Begin a combo off to his side shortly before he becomes vulnerable, then hit him with the 4th part of the combo to finish the fight.
Because Zant's attacks in this phase are hard to predict and he warps away if he's hit with any slash during his chopping attack, it is difficult to elegantly back up the strategy described above if failed. Most players in this scenario opt to spin attack repeatedly and hit Zant with the 4th part of a combo if his spin attack is countered at any point.