The Bowser:
Should Fortress out of Shield alot more. Shield, then push Up+B, then either chase Zelda or retreat to an Edge. Use this out of shield right after Zelda hit's your shield. This will make Zelda a bit more scared to go offensive. Hold the ledge when Zelda is recovering. For now against your friend I think you could use that to bait him into not sweet spotting and running in to punish. However he could eventually start sweet spotting anyways, and screw up your ledge game, if you chose to enter the stage everytime.
Make sure when you do Short hop F-airs, you lcancel them. You don't want Zelda kicking out of shield on you. Also if Zelda tends to block alot when you jump, use the Koopa Claw instead which you did a few times. That's good.
You tried to upsmash Zelda while she was holding the ledge. This would work if Zelda was dumb enough to roll into your charged upsmash. What you should do is run at the edge. And either Aim your forward tilt down a bit so you hit the ledge. Or after you run forward a bit, Turn around and upsmash in the spot you planned on. Because if you run at zelda on the ledge. She doesn't wanna sit there and do nothing. Oh yea if Zelda throws you Down, DI to her BAck.
The Zelda:
Kick out of shield, Naryu's love out of shield, Upsmash out of shield(Less reliable when ur friends learn how to smash DI). I don't think Down-throw to Kick works on anyone who knows how to DI it. You'll find it to be quite useless when you play against people who know how to fight against zelda. Also you'll find, you can't do anything out of a throw unless it's a space animal, or a really low percent medium weight, and you upthrow to kick. Even then it's not garanteed. But if your near an edge, you can downthrow and tech chase seeing how they can tech roll away, and get away from zelda's slowness.
You'll really have to L-cancel your neutral airs on bowser with your approaches. Up+B out of shield from bowser is always nasty. Well L-cancel everything. Forward tilt, and uptilt are good moves, but they should be used sparingly, because If shielded you can be punished. Jab, downsmash, and F-smash on shield are more safe. Not sure how safe F-smash is vs the Fortress out of shield. Even more safe is a L-canceled Spaced Kick, into Say Naryu's love if you expect fortress out of shield.