Zoro and Luffy have undoubtedly received the most hands-on training in a fairly short amount of time, being mentored by two legends.
In this regard, they received a very similar teaching, but in terms of what they learned, there is a distinct difference.
From what we’ve seen of Zoro’s training, Mihawk took a very detached approach when it came to teaching him his lore.
From this flashback, we can tell that after learning the basics of Haki, Zoro was told that there was an extra step and that he would not be allowed to drink until he had mastered the haki of armament.
Rayleigh was much more direct with Luffy, as seen in the multiple flashbacks. Chapter 894 shows a flashback in which Rayleigh uses a haki-covered wooden mace in order to increase Luffy’s skill in Observation Haki. However, he also used deprivation to motivate Luffy, challenging him to dodge 100 attacks before he could eat.
Now let’s compare the two. To sum up, we would say that Rayleigh was much more basic in his teachingsbut that it cemented the groundwork better and made it clear how Luffy could evolve, while Mihawk taught Zoro more advanced techniquessuch as extending his armament coating to weapons and increasing the power of his sword strikes.
Rayleigh and Luffy became close over these two years, and we think Rayleigh really wanted to help Luffy and teach him everything he knew, as he was impressed with Luffy’s character.
Mihawk, on the other hand, is said to have had a very formal relationship with Zoro, since at the end of the day, they’re still enemies battling it out for the title of World’s Strongest Swordsman. It seems to us that Mihawk didn’t really get involved in teaching Zoro like Rayleigh did for Luffy, but instead left Zoro to fend for himself. The injury Zoro received in his left eye may have been due to to the fact that he fought with Mihawk and tried to force himself to learn a new skill.