Okay let's look at how the match will play out.
The standard stage is probably going to have at least one platform which means jigglypuff's rollout is all but useless. on the few stages with no platforms, zelda can pretty easily yank jiggly out of rollout with Fsmaash or parry it with Dtilt and follow up with anything since jiggly doesn't have a single move that can connect at the range she'll be stopped from Dtilt, even if she DOES react in time.
Jigglypuff WILL be approaching. at most distances, Zelda can pretty safely spam din's. Sure jiggly can avoid it, but it's not hurting zelda in any way, the worst zelda can do is break even if jiggly consistently dodges, and it only takes one connection of din's for zelda to get the damage advantage. And it's not like jigglypuff can ever cross that comfort zone safely. She's the slowest character on the ground and her air speed, while the highest in the game, is still not threateningly fast, so zelda has a LARGE comfort zone for din's. And once jiggly DOES get close, she has ZERO moves that will outrange zelda. zero. And her ground game is just awful. maybe she has a good grab range, but it's still not good enough to get past zelda's defensive game and zelda is notoriously one of the hardest, if not THE hardest charcter in the game to grab. not to mention jiggly's ground game has very little versitility. I'd go as far as to say thatl, aginats a good zelda, jigglypuff should fail at least 19 times out of 20 attempting to breech zelda's defenses from the ground.
In the air she doesn't fair much better. Jiggly has better approaching options from the air, but zelda has Usmash. whatever defenses zelda had against jiggly's ground approach, her Usmash is better than all of them at stopping aerial approaches. it lasts too long to spotdodge and outprioiritizes any aproach jiggly could make from any angle in the air (except those so low that zelda should be defending as if jiggly was on the ground.) Sure you can DI out of usmash sometimes, not often, but sometimes. but even then, we still win. you don't take as much damage as you might have, but you take some, and zelda takes none. we win the exchange.
Jigglypuff HAS to rely on zelda making a mistake, which is not a good thing already, but the problem is, jiggly CANNOT keep pressure up once she DOES connect. let's assume zelda makes a mistake and jiggly gets in. well.... so what? Jiggly gets one hit in and simply cannot apply pressure. Jiggly has awful fall speed and awful aerial acceleration which means that, once she DOES pop zelda in the air, it's relatively easy for zelda to avoid jiggly. Not that the air was all that safe a place for her anyway. While jiggly's aerials are all around more reliable in the match than zelda's, all of zelda's can kill jiggly at about 60 damage. And you might say "it's really unlikely that zelda's going to hit jigglypuff with one of those in the air" I say it's no less likely than jigglypuff actually breeching zelda's defenses while zelda is grounded, and you insist you'll be doing that often enough for it to matter...
So looking at that, I mean zelda's just got the massive advantage strategically in the matchup and that's BEFORE you consider their statistics as far as weight and KO power. Jigglypuff has almost no viable kill moves against zelda. Rest kills at low damage, but it's hard to set up for and a miss is JUST as deadly to jigglypuff as a hit is for zelda. Jigglypuff's Fsmash is slow and her Dsmash doesn't have the range to hit zelda so, realistically, you can't rely on those connecting unless you get lucky and zelda is making some serious mistakes. even then, they don't kill half as well as what zelda can do to you. Rollout is counterable, as said earlier and is hardly reliable even without that consideration. DACUS is not good. USmash has okay kill potential, but even with it's slide given by DACUS, it's still pretty easy for zelda just to plain old outprioritize.
Zelda on the other hand, can kill jigglypuff with probably at least 9 moves at damages lower than jiggly could conceivably KO zelda. That's pretty bad considering the fact that Zelda will be doing more damage and have an easier time landing attacks.
Jigglypuff's got one thing on zelda, really, and that's that at certain damages, without good DI, Jigglypuff can use fair to chase zelda too far away for her to recover... but, while that's doable, it won't happen often enough to save you.
Jigglypuff should not be winning this one, it's simply to hard for her to connect and too hard for her to kill especially considering how easy it is for zelda to just whack jiggly off the screen. as long as zelda remains cool and grounded, which is NOT hard to do, this matchup is cake.
I'm not saying this from a purely Zelda standpoint either; Jiggly was my main in melee and I'm still pretty compitent with her in brawl. I've experienced this matchup from both sides and I say zelda clearly has a large advantage. 60:40 is too conservative, it's 65:35 at best. probably no worse than 70:30, but more likely to be 70:30 than to be 60:40
