PokemonBattleFanatic-
Hardcore Paul Fan
Ash-Greninja > Charizard > Blaze Infernape > Sceptile > Snorlax > Infernape = Greninja > Krookodile. Pikachu at peak strength = Charizard. Ash's Pokémon don't yet have the power and durability to compete with regional champions, but I do believe Ash by the end of XYZ had attained skill on par with that of E4s and Champions.
Charizard may not be on par with an elite four but he'd put up one hell of a fight and would last a lot longer than any of Ash's other Pokemon that faced an elite four in the past.Honestly I don't see Ash-Greninja being stronger than current Charizard because when it returned back in BW it was much stronger and it was evident in that little match with Iris's Dragonite but we never saw Charizard used to its full potential since coming back so I'd have.........
Ash-Greninja=Charizard