As far as an HD TAS route goes, getting the grapple hook is unfortunately required as HD has no way of getting to the Leaf without using the grapple hook. You can't zombie hover up since any items you collect while dead don't actually get collected in HD. You can't zombie hover up the outside either as there's no way to heal and get into the top most loading zone of forest haven (which is the highest loading zone on the overworld).
Light Arrow skip in this case would not be faster, as getting boomerang would be a 4 minute detour and Light Arrows take ~1 minute to get. We can however, skip getting the quiver and get past Phantom Ganon using this:
https://www.youtube.com/watch?v=tk-3Tox2Kjw
Also, as SlowKing was mentioning, there is in-fact a way of doing Early Master Sword with simply an Item Slide from the top of Forest Haven. I did it with frame advance on console and then spliced it together to look like real time:
https://www.youtube.com/watch?v=0jLBKV0ipoQ
With all this in mind, this is the fastest route I can think of:
- Skip intro CS
- Superswim to Greatfish
- Superswim to Submarine, get caught, beat FF1 with broken lighting (Beating FF1 is required to spawn the King of Red Lions, otherwise the game will crash in Hyrule 2. The lighting will be broken during FF1 due to the game trying to apply endless night weather effects)
- Spawn at Windfall, get Bombs
- Superswim to Bomb Isle submarine, obtain bottle
- Superswim to Dragon Roost, get Wind Waker
- Catch water in bottle, Rock Skip
- Watch Delivery Bag cutscene, exit to pond area
- Pour water on dry bomb flowers, blow up pond rock (Normal bombs don't work here, only bomb flowers)
- Emter Dragon Roost Cavern
- Go through first room
- Hover up to second story (having an RNG falling rock kill a keese for a heart)
- Go through the final few rooms until grapple hook
- Savewarp out after grapple hook, exit DRC
- Savewarp out to the front of DRI
- Island Hop (an item slide with so much speed you can get to other islands in a single frame) to Forest Haven
- Ledge Clip in and watch Deku Tree cutscene, climb up and obtain Leaf
- Leaf out to highest southern entrance of Forest Haven and perform EMS
- Helmaroc Skip with Item Sliding and Roll Clipping
- Hyrule 2
- Item Slide clip to Hyrule bridge to skip going through the castle
- Barrier Skip
- Item Slide into Ganon's Tower
- Trials Skip
- Obtain Light Arrows
- Phantom ganon Skip
- Item Slide up grand staircase, grand staircase skip
- Puppet Ganon Skip
- Ganon
If there is a way to get the Leaf early discovered in the future, then getting the boomerang would be the ideal option as a first person item. It would also allow for full Light Arrow Skip, Dragon Roost Skip, and Bottle Skip.