Hi, Zelda main here. CF is one of her more difficult MUs, I think, which is saying something, because I think almost all of her MUs are between 60-40 against her and 60-40 in her favor...I was playing with Smash G0d, and after 4-stocking me twice with CF (which he could not do with any of his other characters), we talked about the MU and things I could or could not be doing. Basically, she's combo food. His movement ability is just too much for her to handle.
Dash dance, n-air to approach, up-air combos her for days unless she can get a Love Jump out. Even then, she's left helpless. You HAVE TO BE PATIENT. Fein approaches until she does something laggy, then punish. Zelda has to commit to a lot of her options, so if you can get her to guess wrong, you can take advantage of that. N-air and d-air are both good starters, and up-air will carry her all the way off the stage. Be sure not to get caught by Nayru's, and n-air will fight through Din's.