Can anyone please tell me how you're able to control the boomerang so well that you can hit multiple targets on the return swing, I can't find enough information and imitating other peoples runs isn't help, is it a version thing or something, or is there something I'm missing on the control?

The first boomerang is all about timing. Walk a little bit to the right and angle the control stick straight down during the throw. Weak and strong hit boomerangs work here, but I find weak is easier. You will have to delay your first jump a tiny bit otherwise the boomerang will hook up and to the left of the targets you want it to hit. Wait too long and it'll move down towards the bottom blast zone.

Boomerang 2 is where it gets much harder, but the good news is there's a very easy solution. Are you familiar with how control stick resetting works? Unplug your controller, or hold Start/X/Y for 3 seconds and move the control stick completely to the right and a few degrees down. Release the buttons while holding this angle. This won't make Young Link walk to the left, but it will aid the second boomerang throw. When I say a few degrees down I truly mean it. This is a very light tweak.

If you recentered your controller correctly all you need to do is stand on the very right of the long platform atop the starting chute, smash throw the boomerang left and angle it down/left into the lower left corner. It'll probably take a few recenters to get the angle right, but once you establish that you can get the second boomerang every time with no effort.

Here's a video of the stage zoomed out with the boomerangs connecting how they should for some clarity.

My advice would be to grind this one out. As far as world record strategies go it's one of the easiest with recentering on the table. Even bad runs will end up at about 5.50.

I don't know why I wasn't alerted to this responce 2 months ago, I appriciate the detailed responce and I am going to be attempting this again soon.