Zoro might be stronger in physical strength, and Sanji excels in physical speed, but that's not the point. Zoro and Sanji are equals in terms of battle strengths and role importance in the grand scheme of things. (Let's not forget that while it's true that Sanji fights using his enhanced body, Zoro fights using three really powerful magic swords as extensions of himself. So they're also both equals in terms of battle "enhancements" gained for fights. Your argument is only valid if Zoro could fight 1v1 with Sanji and win the fight without his tools, aka swords.)
