I feel that yoshi's another 50:50.
the nature of his recovery gives us free din's damage a lot of times, so that's nice.
And a hugely helpful thing is that he really can't camp any better than we can. His eggs are BETTER, but both are bad and if you're decent at powershielding his eggs shouldn't be a problem until you have to approach through them.
His weight is nice for juggling with usmash, so that's a plus. and his spot-grab is pretty slow meaning it's not quite as bad for zelda to pressure his sheild. however, if you get stuck ABOVE yoshi, that uair is horrifying.... then again, he's also in a horrible position if he ends up above zelda... though he IS more maneuverable so it should happen less often.
Stages with correctly laid out platforms can really hurt his eg-projectile game giving zelda a slight edge when it comes to who causes who to approach, but more open stages give yoshi better ability to pressure.
Overall, neither really has much of an advantage over the other with zelda being able to rack damage quite well but yoshi being able to kill us at earlier percents. As is usual for zelda, you don't want to give your oponent an advantage because zelda's foes can run away with it pretty well, but yoshi's got a harder time getting one from zelda in the first place than most of the cast, so it's not that bad.
Again I reiterate 50:50