It doesn't look like Zoro stopped Nasujuro's attack on the Sunny, since Zoro was coming from behind.
This scene has many differences to when Sanji intercepted him.
- First difference would be Nasujuro isn't casually walking while slashing, here he was doing a serious attack on the run (we already know his running speed) with a jump and everything.
- Second difference is that Sanji announced his presence and everyone reacted (and even answered) to him... but Nasujuro, who outright ignored him like Gorosei have ignored every attack so far, he was still trying to casually slash Bonney. Here, however, Nasujuro stops his slash on the Sunny and blocks behind himself. For whatever reason he didn't just ignore Zoro (I doubt Zoro can actually bypass his regeneration so this seems like Oda nonsense for the sake of Zoro's hype).
- Third difference is Nasujuro was blown backwards after what appears to be an aCoC clash, instead of immediatelly retaliating with a casual bite that his opponent fails to dodge or even see coming with CoO (Which is weird since Sanji is supposedly much faster than he is and has top 1 in the verse CoO).
One performed like every other strawhat when confronting a Gorosei, the other one is getting preferential treatment (again, as always).
Actually excited for what might happen next chapter between them. I wouldn't be surprised if Nasujuro beats Zoro if the fight is prolonged, he is immortal after all and the Gorosei need some respect. They are top tiers but every reader is looking down on them for relying on their immortality.