*Shrug*
Ivysaur at worse is 65:35 for ZZS. Unknown to most people, Ivysaur does have a glide toss, while small is still a glidetoss, and can lead to many things, especially locking any aerial apporaches that ZZS already has. (Glidetoss down to Sliding UpB is too good) Zamus can't punish Ivysaur as well as most of the ZZS people think they do. SideB isn't much an issue to me as long as Ivysaur keeps the pressure around the direct zone of vulernability that Zamus has while keeping to Ivysaur's range. Zamus' side B, after all, has slow start-up.
And I don't know about you, but Practing with characters that have items like Link, TL, Diddy, or Peach really helps to catch items since you're doing it very often, so Zamus with her armor pieces is no threat to me, and Zamus is in trouble if I catch them.
This applies to Squirtle as well. His glidetoss is, amazing, purely amazing. It doesn't go as far as Zamus or Zelda, but his pivot options can wreck havoc, and due to his small size, Zamus is actually at a disadvantage with the armor pieces lying around, espeically when Squirtle has more of them on his side. Aerials, Squirtle's out-prioritize Zamus' since her aerials aren't fantastic. Just watch out for her grab game because it can kill Squirtle very easily. Pivots and patience will win for Squirtle. 55:45 for Zamus.
Charizard has pure power, and the semi-long range moves to deal with Zamus when applied correctly, including spaced Dair, Fair, Jabs, grabs, and Flamethrower. Do not Flamethrower her Side-B, since she executes the attack faster than Charizard can use Flamethrower. Once again, Zamus's grabs are trouble for Charizard, as well as her juggling combos since Charizard is weak against things that can be exploited for heavy characters. Zamus's smashes are slow, so if the opponent likes to play a power Zamus that uses alot of smash, counter with fast attacks. 50:50