Both Zoro and Sanji displayed amazing feats at this point given the circumstances surrounding everything they did up to this point in Onigashima and how that's going to take a toll on them, with Sanji not getting to catch a break and constantly using up his stamina to help others, and Zoro eventually having to deal with the 2x pain once the effect of the cure he got from Chopper wears off.
Obviously Sanji would not be able to stop Hakai the way Zoro did since he'd have to take the brunt of the attack directly with his body, and he's overall weaker than Zoro anyway, while Zoro would still be able to perform well as Sanji did up to this point, and in the end he will get to defeat the slightly stronger opponent between the two.
Just ignore anyone who says Sanji is stronger than Zoro, and acknowledge Sanji's strength even if he's the weaker of the two. Both Zoro and Sanji are amazing in their own right :cheers: