Since the Zabu nerf, there's been a lot of discourse about whether or not he's usable anymore. I anticipate that this deck will evolve a bit as I test it more, and even pre-nerf this wasn't one of my best decks (to be honest I think the Dracula shell was probably the best version of the Zabu deck). But, I don't think Zabu is that much worse with the nerf and is now basically a better Psylocke/Sera in the right deck (and considering they combo together, could even belong in the same deck).
I'll explain a few of the card choices here:
Spider-Man: So, even pre-nerf, Spidey was a bit hit and miss. In order to truly lock down the game, I needed Moon Girl to copy him, which didn't always work. However, I still firmly believe Spider-Man is a very strong card and when used right can easily win you the game, especially if you have Absorbing Man to double his effect without needing Moon Girl.
Enchantress: Might seem like a weird choice in a deck with 2 ongoing abilities plus Mystique, but she counters opposing Dinos, Morbius, Patriot, Captain America, etc etc. with very low risk to you. If you play her turn 6 (or 7 depending on the situation), as you should in most games, you can even play her in the same lane as Zabu because reducing cost doesn't matter when the game's over.
Aero: Aero is just a fantastic card in general, and I really like her as a way to protect your Dino, or to ensure that, if you're winning two locations already, you win those two locations. Also, Moon Girl > Aero > Aero is a hilarious trick that, while toxic as hell, is a lot of fun to pull off, and can often lead to victory. Speaking of which...
Moon Girl: I don't think I need to explain her, really, but some people scoff at Moon Girl in a Zabu deck so I'd like to defend her a bit here. She's an incredible card in this deck. Psylocke > Moon Girl > Zabu + Zabu even enables the same shenanigans as Zabu > Mystique, for one, but you've also got the famous double Spider-Man, Double Aero, and of course Double Dino that she enables. Even Moon Girl > Double Psylocke is really strong turn 5 because 8 energy turn 6 means 2 4 drops which can be clutch if you didn't draw Zabu. Personally, I think Moon Girl is the rockstar of the deck simply because she enables so many plays that would otherwise be impossible, even with Absorbing Man to try and replace her.
Daredevil: I like running DD in a control shell, which is what this deck is. Since you usually want to play Psylocke or Zabu turn 2, though, odds are you're not playing Daredevil until turn 4 depending on the situation. He's definitely replaceable, but he also takes the guesswork out of Aero or Drax plays (if you sub him in), so I think he's still a pretty strong card here.
And now some replacement cards you could use here:
Sera: I thik Sera could replace Aero in this deck. I haven't tested it, because Aero is just too good to replace, and Dino is needed for the extra power, but she could work to enable some cool stuff turn 6, or even some of the classic turn 5 plays if you can do Psylocke > Sera turn 4.
Absorbing Man: Ideally, you'd replace Jessica Jones with Absorbing Man. I don't have him yet, but he's too valuable to not use. Just being able to copy Spider-Man turn 5 is pretty good if you can make it happen, and beyond that he can copy Aero on turn 6, or Enchantress in another lane for opposing Mystiques. Too bad he can't copy Mystique's ability, but he's so good already it doesn't matter.
Drax/Rescue: These would basically just add more power to the deck. You could replace America Chavez with one of them if you prefer variety to consistency, and considering AC is actually a bad card if you haven't drawn what you need to win by turn 5, they might perform better. I run AC to improve my draws, but there have been times she's been an unwelcome card, and a turn 5 Rescue > anything in her lane is the same power, but you have the chance to draw whatever you need, and a turn 6 Drax, if you proc his ability, is only 1 less power than her.