I think the game I'm going to start off as my first speedrun is going to be Link's Awakening. It's honestly not the Zelda game I know the best, (although it is of the 2D Zeldas), but it was the first video game I ever played, and I still find it really fun to play even now. I've been watching Exo's 1:15:00 run on youtube, and I've picked up some stuff, but there are some nuances that I'm still not really sure of.
Unfortunately SDA forums would provide more help for a 2D Zelda game.