WOW things are becoming rather toxic here lately
Anyway Luffy has always fought the strongest because he is the captain and thats the only reason, Oda always makes it so the villain does not run into Sanji or Zoro because they would win if otherwise, not so much after timeskip as Sanji for some reason didnt match up to Luffy and Zoro's standards but that should be different now since he has the RS and that pretty much balances it out in terms of combat prowess.
Oda has pretty much made it so Zoro never runs into the antagonist in each arc except for Enel who pretty much beat Zoro and Sanji because they had no haki while Luffy had an advantage vs him, but every other time Oda never makes Zoro run into the "BOSS" because Zoro would win. Look after time skip, Hody pretty much got OHKO, CC never ran into Zoro and Fujitora had to intervene so Zoro wouldnt defeat Doffy.
IMO since time skip the power balance of the crew had changed since Zoro had mastered his abilities while Luffy still hadnt and needed more combat to fully grasp his new skills, Sanji had hit a wall and needed RS to bridge the gap and become equivalent to Luffy and Zoro again, i can understand those who believe Zoro was stronger than Luffy after timeskip since the story might be implying it in a sense that it would be pretty much unbelievable for Zoro to beat commander 1 if he wasn't commander level to begin with.
Its more believable to say after WCI Luffy had finally grasped his limitations and abilities and at that point was now on par with commander level enemies, something Zoro was from the beginning while Sanji was still not even close to commander at that stage, but after the Katakuri fight and Sanji receiving the RS the 3 of the were again comparable.
- I mean it has always been that Sanji while not as physically as strong as Luffy and Zoro he is able to keep up because of his intellect and his fighting style that exploits enemy weaknesses allowing him to beat stronger people than him because of it;
- While Zoro on the other hand is as physical as Luffy but his sword style allows him to be lithal and can beat opponents faster that way and because of his personality he is always serious from the get-go thats why he would never lose to people weaker than him or get overcome by emotions like Luffy
- Luffy on the other hand always starts of slowly and comes across as playful because unlike Zoro he never goes for the win from the get go he plays around and then ends his opponents after he overpowers them with his will
In regards to Luffy and Zoro for me Zoro has always been the stronger of the 2 in a fight but because of Luffy tenacity and his ability to get stronger as he fights it wouldnt matter if Zoro was the stronger fighter since Luffy wouldnt lose because of his abnormal will, the 2 of them have acknowledged that they dont know who was stronger and they both believe the other would never lose a fight, but because Luffy is always been pushed in fights he tends to pull away only for Zoro to catch up before the next arc and thats how its always been and i dont see it changing. This whole argument that Luffy fights the strongest and Zoro doesnt meaning Luffy is stronger is a stupid argument, yes Luffy fights the strongest and always ends in an extreme diff fight, while Zoro fights the 2nd strongest but because Oda doesnt want Zoro to OHKO he always gives the enemy an advantage and handicaps Zoro.
Anyone who has been paying attention this past 970+ chapters would know that Luffy and Zoro are equal(since they said so) and that Sanji's technical style and his intelligence makes him equally as dangerous, this has started to change as it looks like Oda is now making it obvious that Luffy≥ Zoro>Sanji with all this haki upgrades. Haki was a cool concept but recently im starting to hate it since it cheapens DF abilities and the different combat styles in the world, right now its becoming the one with stronger haki always win and i hate that