Well first off, this is interesting, being pretty much a tournie deprived Brawl player and seeing all the expert opinions.
Second off... The purple...my eyes...
Third off- Noob thoughts on zelda.
Zelda is mainly a spacing reliant game in which she has nearly free targets with her Din's fire to anything in front of her, and the ability to reflect projectiles with no lag.
Most Zelda's I fight, and thats not a whole lot will spam Din, and then I can SH or hop and aim down with my laser. The laser then bounces off the ground, hitting zelda, stopping the din's controllable release. If they realize I'm doing this, they will either aim it at ROB, or aim it at the ground or release it early. If they aim it at ROB, and ROB's laser connects, they lose control and it explodes in the air behind and above ROB. If they aim it at the ground, ROB is high enough that when it detonates on impact with the ground it won't hit ROB because he jumped. If they stop the Din and go to cast Nayru, and they cast it successfully, bouncing the laser, it will bounce back and hit the ground. (This is really hard to time and you have to jump VERY early in this, otherwise you will get hit with the fire exploding before you finish your laser.)
That being said, ROB has the ability to utilize his range attacks at a faster speed then Zelda does, and whenever its a faceoff between the two, I think ROB would have the upper hand.
Next is Zelda's aerials, which are pretty lackluster making her easily camped and gives her a harder time spiking.
I really think that MK and Pit can be difficult at times, because they have fast starting aerials, whereas ROB has very slow aerials such as his nair, dair and bair. My main tactic against those 2 is just to stay away from their kill moves, aerials and use Pit's arrow spamming to my advantage.
Well those are my thoughts as a non-pro. Anyone more experienced want to comment?