Even if People believe Luffy is stronger than Zoro now
You cannot Deny that Zoro started Post-TS Superior than Luffy
The guy was since then strong enough to do all these Roof Feats but Luffy had to improve his Gear 4, learn Two new CoA Techniques & unlock Future Sight & also CoC imbued attacks to finally be here
So since it's a Fact that Zoro was for quiet a long period superior than Luffy then it's not far-fetched to say Zoro is stronger than Luffy.
After all Luffy is the guy who Recruited Best Chef & Best Doctor & Best Historian & Best Shipwright & Best Musician ... etc
So it's obvious that he also Recruited "Best Fighter"
And this is why Luffy multiple times said "Zoro can handle anything"