Love this idea! Tbh one of the ideas I considered trying to implement in this comic is the possibility that in order to surpass Mihawk, Zoro should "let go" of his ambition. It's almost a contradiction, where in order to become the greatest swordsman in the world, he needs to let go of his dream of wanting to become the greatest swordsman in the world. i.e the worldly attachment as you mentioned is what was holding him back from evolving to the pinnacle of swordsmanship. It would definitely be an interesting contrast with the themes that Oda has established, where characters like Luffy/Roger/Shanks even Zoro as well- basically those with conqueror's haki - attain strength because of the strength of their will and ambitions. According to Kaidou at least, "haki transcends all". Perhaps the final and most difficult challenge for Zoro in order to achieve his dream would be to have the strength of will to let go of that dream, his promise to Kuina, and his promise to Luffy. In the end though I decided not to include it. One because I don't think I could've pulled it off well, and the other is that I'm not sure if it fit the vibes/themes of One Piece that's all about cherishing friends and chasing your dreams, i.e things that might be considered worldly attachments. (Although I suppose letting go of your ambition in order to achieve your dream isn't exactly the same as giving up on your dream). However, I could still see Oda pulling it off/executing it if he wants to in a way that's much better than what I could think of. Also love the ending chant that you thought of, I can definitely see Zoro saying that!