Zoro: his swords
Sanji: his body
Each being the main focus of their training and strength ever since they were young. Sanji being a martial artist, zoro a swordsman, and luffy being a devil fruit based brawler
By the time they made it to sabaody the improvements they made were massive
- Luffy improving his creativity with his fruit and developing gears
- Zoro getting better/stronger blades to try and master. Along with learning more swordsman techniques
- Sanji somehow developing Diable jambe and having some sort of heat/fire manipulation
During the 2 years of training they all went even further to improve themselves
- Sanji training under ivankov specially focusing on improving his body. Not only through being constantly on the run 24/7 but through the cooking. Sanji learning attack cuisine recipes all of which are made to build one’s body. With him having way better mastery over diable jambe and his fire power
- Zoro training under mihawk obviously to improve himself as a swordsman. Zoro seemingly gaining a better mastery over his swords especially shusui. With that blade in particular becoming his main go to after the timeskip. Theory but I do think he might have completely mastered the blade during his training with mihawk. With in the process it potentially giving him a similar scar it gave ryuma
- Luffy’s training with Rayleigh might have been more haki focused but he still improved massively when it came to his mastery over gears. Even developing a new gear during that time
As for haki the 3 were the only strawhats to train their haki during that period. Each of them using it in conjunction with their main weapons. (Specifically armaments)
- Sanji enhancing his body and diable jambe
- Zoro his swordsmanship and the swords themselves
- Luffy also enhancing his body along with using it perfectly with his fruit
As for where they are now and if their path of growth has changed? Not at all really
- Luffy: ever since his training with Rayleigh haki has had a big emphasis on his focus but like I said haki doesn’t really change one’s fighting style just enhances. After Rayleigh tho he has learned an advanced technique for each path of haki with future observation, barrier + penetrative armament, and conquerors coating/infusion. His his last and biggest power up being him awakening his devil fruit. With like g4 it seemingly being a perfect blend of his fruit and haki
- Zoro: his main power ups have been enma and unlocking conquerors. With him using and mastering enma he is able to drastically enhance his haki output with it. With conquerors he can coat his haki slashes with it to boost his power further
- Sanji: he did initially get the raid suit in wci but destroyed it so it doesn’t really matter. What does matter is that him using it made him unlock his exoskeleton. The exoskeleton obviously making his body better in every way. With the exoskeleton and his haki he was able to unlock ifrit
