I'm going to try to summarize that video because it's very long and, incredible as his accomplishment is, Kaztalek's commentary is really annoying. It's full of rhetorical questions like, "But how am I going to get the zora eggs without bottles??? Stay tuned...". My summary will have some gaps in it because although I've played Majora's Mask, I'm not very familiar with speedrunning techniques in the game.
• Uses grandma's stories to fast forward to dawn of the final day, then dances with the scarecrow to make it night.
• Backflips out of Clock Town and goes to Goron Village to pick up the Lens of Truth, which he later uses to pick up the Goron mask. (The Goron Mask can't be obtained without the Lens of Truth.)
• Suicides to return to Clock Town.
• Gets magic from the fairy in North Clock Town.
• Buys a bomb bag to use bombs for extensive hovering later on.
• 21:43 - Pauses to equip bombs, the Lens of Truth, and the Ocarina of Time.
• Runs to the swamp (still a deku), gets to the giant octorok, drowns, gets hit by a rock spit by a small octorok which sends him flying past the giant octorok into the area with the Deku Palace.
• Does some creative wall clipping and jumping and is shot by a Deku to put him on the higher level of the Deku Palace. From there, he straightforwardly picks up Sonata of Awakening.
• Heads to Woodfall to use the Sonata of Awakening.
• Heads back to Clock Town to get the Song of Healing. Uses some giant dragonflies and a similar trick to earlier to clip past the giant octorok blocking the path.
• Now in human form, gets the bomb mask to allow him to pick up the large bomb bag. Buys bombs and does an out-of-bounds warp at the fairy fountain to send him back to Woodfall.
• Does some bomb hovering to get to Woodfall Temple.
• Gets the bow.
• Uses some bomb hovering and an out-of-bounds trick to get to the boss room in Woodfall. Defeats Odolwa.
• Plays Song of Time. Picks up rupees and buys more bombs.
• Staircase (bomb) hovers over the fence to Great Bay. Gets the zora mask.
• Fairy warps to Ikana Canyon.
• Uses extensive bomb hovering to get up to Stone Tower Temple. This portion takes over ten minutes. He uses a few enemies to replenish his bombs along the way.
• Uses bomb hovering to get to the light arrows.
• Flies back to Clock Town. Uses staircase hovering to reach a hidden owl statue. This is used for something called "mayor's warp", which I don't understand well.
• Goes to Romani Ranch to pick up Epona. The mayor's warp, an owl statue, a stored Song of Time, and a gossip stone combine to trigger something called the "zeroth day glitch", where the day is returned to the first day's state without interrupting progress. This allows him to get Epona's song.
• Uses Song of Time. Picks up more bombs.
• Goes to the mountains, obtains the Goron mask (recall that the Lens of Truth is needed).
• Goes to Snowhead Temple. Staircase hovers all around it to pick up the flame arrows and eventually reach the boss room.
• 1:38:25 - Pauses the second and final time. Equips light arrows, the goron mask, and the zora mask and then equips the fire arrows over the light arrows while triggering the zeroth day glitch again. This allows him three seconds to use the fire arrows before they are permanently replaced with light arrows. Uses the fire arrows to thaw Goht.
• Kills Goht with light arrows.
• Returns to Termina Field and loses his sword to a bird.
• Saves at an owl statue in Clock Town as zora.
• Copies the save, loads the second file, goes to Romani Ranch, picks up Epona. Saves at the owl statue while on Epona in the second file.
• Resets, loads first file, now on Epona as zora in Clock Town. This cancels zora's B button (now he can't use the boomerang fins) and allows him to use the B button for items depending on the state of the B button at certain times (I'm a little unclear on the details of this). Basically, if the B button says "Pound", he can use the zora's B button to instead drink Obaba's drink and obtain a bottle for catching zora eggs. He uses a similar trick with the goron mask to store the ocarina as the goron's B button.
• Begins the Easter egg hunt at Pinnacle Rock. He also stores the Song of Time, which allows him to clone the first egg. I'm not exactly sure why or how this works.
• Deposits the first egg and clones it by activating the stored Song of Time. This also resets the Pinnacle rock eggs, so he now needs the three Pinnacle Rock eggs and two Pirates' Fortress eggs. These are obtained one by one. To get on the aquariums in Pirates' Fortress, he jumps off a chest in one room and a barrel in another room. The entire egg quest takes about 30 minutes...
• Something about depositing bugs at a gossip stone allows him to use the ocarina as a zora. This lets him play New Wave Bossa Nova. Saves at a nearby owl statue and resets.
• Transfers Epona from the second file for the third time. This allows him to use the zora's boomerang fins again.
• Gets eaten by a like-like while it's on land and he's underwater, then kills it. (The exact sequence of events here is hard to follow.) This paralyzes him except for punching, which moves him forward slightly. Also, the player's y position is preserved, except when they move uphill. This allows him to hover over various terrain to get up high enough to mount the tortoise.
• In the Great Bay Temple, clips through the wall to get to the boss room. Kills Gyorg. Flies to Stone Tower owl statue.
• Does a hover glitch to reach the background area of stone tower. Runs into position to shoot a light arrow at the gravity inverter.
• In inverted Stone Tower Temple, hovers off of some poes to get out of bounds and reach the boss room. This takes about six minutes.
• The rest is straightforward. Kill Twinmold, uses Oath to Order to get to the moon, kills Majora. The end.