Peter Jackson seems like the obvious choice because he's already directed the greatest medieval-inspired fantasy films of all time, but imo it's a different type of fantasy. Zelda is about one guy quietly going through dungeons with moody music, encountering all sorts of crazy monsters while solving puzzles. It's less like The Lord of the Rings's big battles and more like Legend, Labyrinth, or Willow, which are more about a few characters going from one bizarre encounter to the next. Since the directors of those films are Ridley Scott, the late Jim Henson, and Ron Howard, Howard or Scott seem like good choices to me. I generally prefer Scott's work but I don't know if he's still interested in the fantasy or sci-fi genres. Ron Howard's daughter Bryce Dallas Howard has directed some of my favorite episodes of the Star Wars TV shows so maybe she'd be up to it? Scott would be my choice since Legend feels so close to a Zelda movie already.