Organically Sanji was never meant to be Zoro's equal in combat, they often times compete like two siblings do trying to figure out who is "Better" but it was never about individual strength.
Sanji and Zoro have never had a fight, One Piece data books that are either reviewed or straight up written and even referred to in different SBSs have Zoro and Luffy being equal in combat and Sanji being a level behind.
Worst Generation is a generation that was meant to rule the new era and Sanji was not part of it, while Zoro was. Oda even went out of their way to have them actually fight and both wanting to know who is stronger where as in Zoro's mind it is clear that he is stronger than Sanji. And that stance is supported by both gag moments like Zoro saying he is worth 2000 men and serious moment like Zoro taking Luffy's pain and knocking Sanji out claiming it is warriors job to protect and not cook's.
Even recently among worst generation and new generation in general 5 people were separated facing two emperors, the gate keepers of current generation and those 5 people are Luffy, Zoro, Kidd, Law, Killer and Sanji is not one of them. Zoro is often compared to his captain by bystanders as well.
So even if you don't want to subscribe to feats which heavily favor Zoro, portrayal, hype, in universe statements and external source material all points to Zoro and Luffy being comparable in combat and not Zoro and Sanji. It almost diminishes Zoro's worth as a character if he is close to Sanji in combat.
Sure, I will just follow the reasoning I always follow in this regard:
If Zoro is comparable to Luffy we've all wasted twenty five years of fighting potential with Zoro facing a second-class adversaries; awesome writing there, certainly. Unless, of course, the hierarchy is just like Lucci, Kaku and Jabra, as Oda made it obvious back then, and he will keep feeding this rivalry so the fandom increases its activity (which, again, is of economic interest for his business).
And let's get this right: I do think Zoro is stronger, but I find it highly unlikely that Oda has been working on their rivalry for so long (not only with gags but with actual versus of incredibly close enemies and all kind of hints, like Mohji and Cabaji) only for Zoro to be hugely stronger than Sanji and equal to Luffy. That's just inconsistent and makes zero sense from a writing point of view.
Oh yes the mean zoro fans with all their feats and potrayal makes it hard to put Sanji on zoro level huh. Curse the day the zoro fans was born
Then you had Oda straight-up comparing Luffy, Zoro and Sanji to Lucci, Kaku and Jabra in the most explicit ranking possible (the only ambiguity actually discussed the power difference between Kaku and Jabra, not Lucci). But certainly "feats" and "portrayal" are relevant here even though the first thing Oda does after timeskip is putting them both in a fighting contest with the Pacifista.
I'm sure Oda wants the community to believe Zoro is miles ahead Sanji and not very close, because that's the narrative he has been reinforcing and not the rivalry that fuels fandom activity to its highest.