Falco: Really no reason for the Falco to ever lose this MU unless they overextend. If their pressure isn't tight enough, or they try to reach too far on combos, they can be grabbed/upsmashed OoS/kicked offstage without a jump. This will be a recurring theme for characters fighting Zelda, but all Falco needs to do is stay patient and camp her out with lasers. Once he is confident that he recognizes the Zelda's shielding habits, he can laser grab when she will stay in shield and punish aerials OoS with nair/shine/upair/dair depending on the spacing and whether the Zelda fullhopped or shorthopped. One good thing about the MU is that it's hard for Falco to confirm a kill off an edgeguard. He has to stay near the ledge to cover the sweetspot option, which makes it hard to cover an up-B far into the stage with an actual killmove. If you can avoid dairs offstage (and fsmashes which shouldn't land anyways), you will be able to live for a long time most stocks, whereas he might **** up once at 30% and get kicked off stage, then edgeguarded, and that's why the MU seems rather doable. Again, if he's exceedingly patient, there's no real reason for him to get hit. Also, dtilt is probably the most underrated killmove for him in the MU. Oh, and you can CG to somewhere around 50% (don't know exact percents).Here's what I tend to think of Zelda's matchups:
Vs Falco and Marth, I think Zelda can compete (but it's tough)
Vs Peach: Zelda can meaningfully compete
Vs Ice Climbers: Zelda can meaningfully compete,
Vs Jigglypuff: Zelda can meaningfully compete, almost feels even
Vs Samus: Feels about even
Vs Luigi: Zelda can meaningfully compete, almost feels even
Vs Donkey Kong: Zelda has an advantage
Vs Mewtwo: Zelda bodies Mewtwo
Vs any character below her on the tier list, I think she wins handily, except against Kirby (quite disadvantaged) and Pichu (maybe slight disadvantage but even-ish).
Marth: His dashdance just destroys Zelda, but she will live a very long time if she can avoid tippers and dairs offstage. I've played PP's Marth, and he was amazing at confirming dairs so that I rarely lived past 100%. Those were rough games. One thing to note is that you can beat his fsmash with your kick when falling down, so long as you time it perfectly, because of how he extends his hurtbox with his hand before the actual hitbox comes out. You can also punish not perfectly spaced fsmashes OoS with kick. As far as the neutral goes, if Marth just pokes you with dtilts and grabs when you shield, you just lose, there's no way around that. If they ever try to nair approach, you can dash attack it. Usually you want to slowly close in on them and take stage presence if they'll allow it, then try to dash attack their dashdance when it's hard to react to. You're gonna lose the neutral all the time tho basically, that's just how it works. As far as edgeguarding goes, I like to ledgestall with Farore's until they are close, then comes the mixup. If they up-B to the ledge early, you can neutral get up and cover it. If they up-B high, you can neutral get up and turnaround dsmash. If they up-B to the ledge late, that's when you have to roll to cover it. If they still have their doublejump and airdodge onto the stage, you just have to take a nair or kick them to the other side usually. In short, his neutral destroys yours, you have to bait and have better punishes. Dthrow to kick works if they DI in only, which can be good if your back is facing the ledge.
Peach: Turnips win the MU. When they don't turnip camp you, you can contend with her aerial game because your kicks are disjointed but you have to have a good idea of when they will use their moves. It's really hard to react to an incoming FC fair and still have time to get airbourne and space out a kick, so you're usually forced to shield and buffer roll since they will usually dsmash/grab after. If you know they will jab afterwards, you can drop shield and CC jab(s) into dsmash, but that's about it. Also, Nayru's is not that good, sorry. Good Peaches will either throw turnips from the ground and jump over them to punish or throw turnips from the air and fastfall to float underneath. It can be good when they have already committed to their float height. This is one of those MUs where Din's Fire is actually usuable. Because her recovery is so good, but she's also relatively slow, when you send her offstage, you can limit her options with Din's Fire. It rarely hits because it's a terrible move, but it's no risk, and I have legitimately gotten Din's Fire into kick on Peaches in tournament. Also, kicks are a perfect spacing to punish dsmashes, so they have to think twice before dsmashing on platforms and on shield. Again, turnips just straight up win the MU if they camp.
ICs: Similar to Peach, they win by camping projectiles (in this case ice blocks). If you let them get a lead, you should lose. There's really nothing Zelda can do to get around ice blocks and desync'd blizzards. if you get a lead however, they are forced to approach. It's similar to the Luigi MU in this scenario, where fsmash is a good anti-approach (even better against ICs than it is against Luigi since Nana is almost guaranteed to get hit by the last hit), but you have to know when they will approach. It's punishable on whiff, and it's still punishable on shield but much harder. Oftentimes, you will be able to stuff their OoS approach with dsmash. Nayru's is also situationally good. It's easily punishable on whiff and on shield, and getting grabbed means you're dead, so most of the time, you should not use it. However, when they aren't in a situation to punish with a grab, it can be useful and often separates them. Ex. SoPo and when you know them shielding it will push one of both of them off onto the ledge. Edgeguarding can be surprisingly tricky because of how slow Zelda is. With their ability to lean forward and back with the side-B (and raising and falling), it often leads to sourspots and whiffs due to the precision needed with kicks. Just something that can be practiced, and it's helpful if you can pick up on their recovery habits.
I'll do some more later.