In the 2nd phase of the fight, the player normally must wait for Ook to deliver bomblings to use on Diababa. However, one can juggle bomblings from the 1st phase (or simply use bomb arrows if available) to avoid having to wait for Ook. While Ookless with bomb arrows is as trivial as shooting Diababa with a bomb arrow to knock it down, shooting again once it's on the ground and vulnerable, and then repeating for a second cycle, Ookless without bomb arrows requires attention to position, timing, and targeting and will be the focus of the remainder of this section. This trick is useful in all categories that fight Diababa and saves over 30 seconds over doing the fight normally.
Note that Ookless is possible because the bomblings' countdown timers reset when the boomerang picks them up.
Use the boomerang to target the middle bombling and then the left baba head, then release the boomerang. While waiting for the boomerang to reach its destination, move Link to the edge of the water near the center of the arena.
After the left baba head's explosion cutscene, use the boomerang to target the middle bombling and then the left bombling, then release. This will bring these two bomblings to Link for use in Phase 2.
While the boomerang is bringing the two bomblings back, target the bombling on the right and wait. This bombling is not always targetable at all points during the boomerang's flight, but one reliable way to target it is to press and hold L to target the baba head on the right, wait until the boomerang has nearly returned and the camera has panned farther right, and then quickly release and press L again to switch the target to the newly targetable bombling on the right.
Once the boomerang returns to Link, continue targeting the bombling by holding L, press and hold the boomerang button to drop the bombling that ended up in Link's hands, walk right a small amount (still holding L) to avoid picking up the pair of bomblings with the boomerang, quickly release and tap L to add the baba head to the boomerang's targets, and release the boomerang button. This will leave two bomblings on the ground and use the final bombling on the right to kill the remaining baba head. Link will be teleported to the same starting position by the cutscene that follows, so his position entering the cutscene does not matter.
If the two bomblings on the ground were placed correctly in Phase 1, then the mid-fight cutscsene will teleport Link to stand right behind them. At the end of the cutscene, hold target, hold down on the control stick, and mash the boomerang button so that Link will throw the boomerang and begin backwalking as soon as the cutscene ends. This will catch the bomblings in the boomerang, resetting their timers but not hitting Diababa.
While the boomerang flies, backwalk to the correct position and then stop and wait for the boomerang to return, still holding L. The correct position can be eyeballed (see video) or found with an audio cue: The Phase 2 music begins with 4 repetitions of "DAAA da," and stopping the backwalk between the third and fourth repetitions (timing not precise) will put Link in the correct position.
Once the boomerang returns to Link, press A (still holding L) to throw the bombling in Link's hands, then backflip and release L. Enter first person with the boomerang, press R to target the bombling that is closer to Link, press L while still facing downward to target Diababa's main head, and then release the boomerang. Note that this will only work if the R-target is on the bombling itself, not on the ground nearby.
Without moving, enter first person with C-Up and look along the right side of the arena towards the waterfall. Of the two bomblings currently caught in the boomerang, one will hit Diababa's main head and the other will return with the boomerang. Once the boomerang returns and while Diababa's main head is falling, throw the boomerang towards the waterfall to pick up the second bombling and put it out of the way for step 5. NOTE: If both bomblings explode during step 4 or one of the two side heads lunges and eats a bombling during step 3, then Link's position after backwalking in step 2 was incorrect.
Once Diababa's head has fallen and the eyeball is exposed, deal damage to it quickly to complete the first cycle. With Master Sword, only a jump attack, spin attack, or rollstab is required. With the Ordon Sword, do a jump attack + quickspin. This damage must be dealt before the boomerang returns with the second bombling to prevent the bombling from exploding on Link's sword or Diababa's eye.
The boomerang will now return to Link while Diababa's return animation plays. Enter first person with C-Up and aim the camera upwards until Diababa's head is roughly in the center of the screen. Once the return animation is over or nearly over, tap the boomerang button to throw it and hit Diababa's head with the remaining bombling. Note that it is possible to throw the boomerang too early, causing the bombling to explode on Diababa's head before it is vulnerable, wasting the bombling. The bombling will also sometimes not hit Diababa's head at all; if this happens, just try the throw again.
Repeat step 5, minus the strict time constraint, to finish the fight.
In Phase 2, Ook takes a long time to come out with the second bombling if doing the fight normally because Ook is delayed substantially when Diababa falls from the first hit. It is possible to avoid this, saving 16s over a casual Diababa fight and losing 14s to Ookless.
Kill the two Diababa Heads as quickly as possible without preserving bomblings. It is possible to target the baba heads quickly with L if in the right position; see video.
Boomerang the baba heads to save 3s, as Ook will not come out until they have both attacked, and this causes them to attack faster.
Catch Ook's first bombling in the boomerang and let it return to Link.
Throw the bombling forward and wait a small amount of time, then boomerang the bombling on the ground to Diababa.
If done correctly, Diababa will fall towards Link as Ook starts coming back with his second bombling.
Once Diababa's head has fallen and the eyeball is exposed, deal damage to it to complete the first cycle. With Master Sword, only a jump attack, spin attack, or rollstab is required. With the Ordon Sword, do a jump attack + quickspin.
Boomerang the second bombling from Ook to Diababa and deal damage again as described in step 5 to finish the fight.
If not attempting Ookless, begin Phase 2 by throwing the boomerang at the two side baba heads. This will cause them to attack sooner, which will in turn allow Ook to appear sooner, saving 3 seconds.
Bombing Diababa's main head very shortly before or as Ook is making its noise to indicate that it will swing across the arena for the first time will result in the camera changing to look at Ook for its cutscene, but Ook won't do anything while Diababa's head is knocked down. This is a temporary softlock that is cleared when Ook next swings across the arena, which is after Diababa picks its head back up and attacks Link off screen some more.
Because bomblings that Link can equip are active during cutscenes, placing a bombling shortly before entering the camera lock of the temporary softlock described above such that the bombling will kill Diababa during the camera lock will result in a full softlock, as Ook will never attempt to swing across the arena again with Diababa already dead.