Ok, stages. There are a lot of tournament viable stages and different matchups or playstyles play a big role. I'll try and give some preliminary thoughts on each.
Yoshis Story: Tiny stage, which is good for Zelda's early kills and lack of mobility but bad for her floatiness and zoning. Reaching up through the platforms is nice and Zelda's platform techchase is phenomenal. I'd say this is a great Zelda stage in ALL matchups (yes even Marth and Fox), but not if you like playing a defensive Zelda.
Warioland: Tiny stage, read Yoshis Story for elaboration. Due to the possibility of opponents landing on the top platforms I find she has trouble juggling (since the middle plats are directly underneath, making her vulnerable as she jumps up to meet the opponent). As such, I don't like this stage as much as YS but I think its still great for her. Again, great Zelda stage in all matchups, but not for defensive players.
Castle Siege: Tiny stage but decent blastzones. Would be good for her lack of mobility but the way the stage and platforms are laid out make pressure difficult to apply. I find reading opponents movements and limiting their options easier on YS and WL. Platforms are also too low to get any good techchases, opponents will be able to act before you've finished your first move lol. I don't think this is a good Zelda stage, but it is a bad stage for many other characters so still consider it. Don't ever play this stage vs Marth *shudders*
Metal Cavern: Similar to Castle Siege but with a different platform layout. I like this platform better as I find it easier to read where opponents are going with it (whether or not they are using it) since it covers center stage and is large. The high ground is a problem for Zelda on both stages since she has nothing that hits at an angle. Not particularly good for Zelda, but many other people hate it so consider it.
Green Hill Zone: Small stage, small blastzones, but the proportions have the top blastzone further than normal. Good against any character you plan to juggle due to usually 0 platforms, bad against projectile users because there's nowhere to hide. The platform often saves people from juggles or gives others an extra recovery opportunity, but it isn't of much use to Zelda. Furthermore, you can't teleport off it since it moves and you can't drop down at any point but the apex or bottom due to how slow she falls (it falls or rises faster #icrievritim). The apex means she has to come down from super high and the bottom is where they are pressuring you already to not come down. Ugh. Good Zelda stage against about half the cast due to juggles and ease of killing, bad otherwise.
Fountain of Dreams: Pretty much the same exact size as GHZ. People think the top blastzone is much higher but the stage is actually centered high up in the blastzones. I think this stage is great for Zelda because the moving platforms give her great options through them, the stage is big enough to use Dins and teleport, and the stage is small enough to go ham with pressure. Great Zelda stage.
Battlefield: Slightly bigger than FoD but otherwise very similar. The blastzones are average. Due to the fact that the platforms don't move, the stage is slightly less open than FoD. Also you can't hit through the platforms as easily. I find it easy to read people on this stage due to how platforms interrupt movement (or enable it, which makes people ALWAYS use them for movement and still get read). Once again, platform techchases are a breeze here. I am always happy to go to this stage as long as I can't get super camped from the top platform (looking at you, Snake and Tink)
Smashville: Pretty much the exact same size as Battlefield, but with one moving platform instead of 3 static. I find it harder to read opponents when there are no stage features to base decisions off of, and nobody seems to care about the platform here. As with GHZ, the platform stops your juggles but doesn't let you techchase and gives opponents an extra recovery option that you usually don't use yourself. I think this stage is just ok for Zelda. Use it against characters you want to juggle, but that's about it. Not too bad though.
Yoshis Island: I think this stage is pretty bad for Zelda. The large, long platform lets enemies easily circumnavigate your Dins, the bumps make it difficult to teleport cancel, the ghosts give enemies recovery options but not you, the fly guys eat your Dins, and you can't teleport off the moving platform. Fortunately, everyone else is bad here too, so I don't bother banning it. I just think you should never pick it.
Lylat Cruise: Perfect for some matchups. The frequent low platforms make enemies readable and let you control a lot of space with Dins. Especially against projectile heavy characters, this is a great stage. It also helps that you should never get caught under the stage if you are good at recovering, since you can pick any combination of angle and timing that you want.
Skyworld: A very open and somewhat large stage, I think this is a very good stage for Zelda. Her platform techchases are amazing here, she can run and camp super easily, and opponents will get caught under the stage when she won't. Due to your ability to run and camp here, opponents will be forced to approach. Since there are no platforms on the main platform its easy to wall them out there, and since the main platform doesn't reach under the side platforms its easy to wall them out there. Large blastzones keep you alive, but opponents are easy to edgeguard. Just don't fall for them using a side platform, should be easy to cover both if you use Dins. Fantastic Zelda stage.
Pokemon Stadium 2: A very open and large stage but with close blastzones. This stage is terrible against anyone you want to juggle due to the locations of the platforms. The large stage means opponents will survive your attacks from center stage but the close blastzones mean you can't use your recovery. This stage is very good if an opponent has to approach you and isn't very quick about it, as you can use Dins and teleport to your heart's content. Not a fan of this stage, but it has its uses.
Distant Planet: PS2 but with leaves and bigger blastzones (I think?). The leaves help opponents recover and retreat from the middle platforms, while they just get in Zelda's way due to how the droop prevents her from dropping through them immediately. Slightly worse than PS2 for her, IMO.
Final Destination: Really big, really open. Great if you want to juggle someone full to death. Otherwise terrible for reading opponents or blocking off paths with Dins. The stage is also so big that it is difficult to pressure opponents. My least favorite stage by far, I'm glad people ban it against me.
Norfair: Final Destination but with a slightly smaller stage and platforms high enough to camp on and do nothing else. The platforms also move really slowly so its hard to tell if you can teleport down from them or not at any given moment. This would be my least favorite stage if it were as big as Final Destination, but at least the size is more to Zelda's liking.
Delfinos Secret: Final Destination but with interesting and usable platforms. Great if your opponent has to approach, and following opponents up into the air is great for juggles and early kills. Use the platforms to block off more space than usual with Dins. Other than that, just an ok Zelda stage.
Dreamland: Triplat layout allows Zelda to get great platform techchases and ladder combos while also effectively blocking paths with Dins. Size of stage lets Zelda teleport and throw out Dins with ease. Size of blastzones means you should never die. You can't reach through the platforms but neither can anyone else, so w/e. Wonderful Zelda stage unless against someone who can camp the top platform hard (ugh Snake and Tink)
Bowser's Other Castle: Haven't had much experience on this stage. Blastzones and stage size smaller than Dreamland and middle platform lower. Otherwise pretty much the same as Dreamland.
