I do remember getting EXP when repeating fights, since you definitely can, so yeah...you could. Although if you ask me, as long as you keep playing as Zoro after you unlock him, you'll level him up enough to not struggle THAT much as you keep playing.
Thanks for reading!
That's cool. Just like levelling up your Pokémon's by fighting and winning battles again. Some people hate this type of levelling up but I love it...lol