No one’s saying Zoros not acting as the VC here. The point is Nami and Chopper stopped arguing with Zoro after Sanji said he’s right. Then Zoro just had to convince Luffy alone because the crews not going to disagree with both of them.
And then in the same chapter Chopper doesn’t try to appeal to Sanji when Usopp is trying to come back. It’s only Luffy and Zoro’s opinion that matters.
All Sanji’s comment does is confirm that he thinks Zoro’s in the right. It‘s not portrayed as a turning point at all, and it’s a minor part of a chapter that is all about Luffy, Zoro and Usopp.