FTL. Oda said he was fast enough to be invisible, as in no light reflecting. Not just the disappear reappear movement type speed most characters do. But continuously moving at the speed of light to keep it up. I don't get why even this has to be a debate. Zoro is stronger, Sanji is faster, they're supposed to complement each others strengths and weaknesses.
1. The same was said for nichiji in base when hebused stealth on sanji.
2. The same is said for those whom can use soru form pretimeskip.
So your point is mute. Keep trying though