After entering the fight slash the first green Spinut then roll into the middle and spin attack.
Start by killing the bug on the left and continue into killing the second and third bugs on the left. After that run to the other side and kill the final bug on the right.
Once the final bug is killed try and run to as close to the whirlwind chest as possible during the bugs death animation.
Start by waiting for the mothula to attack, once it attacks use the whirlwind on the skull then hit it with one spin attack to kill it in one hit.
Try and kill the mothula in a direction close to the door so you are able to pick up the rupee it drops in the quickest manner.