Zoro and Tashigi's relationship is so interesting to me. Specifically how Zoro interacts and treats her throughout the series.
Like when he first meets her in Lougetown, it is so clear that he is not fully over Kuina's death based on his reaction to realizing that Tashigi resembles her. And he's not emotionally mature/intelligent enough to process the complex feelings that come with seeing a person who looks like his childhood friend and rival. So he resorts yelling and claiming that she is copying Kuina, despite the fact that that is illogical. This is also the first time we see Zoro holding back during a fight, because its clear that he can't handle seeing even someone who looks like Kuina die. Tashigi does call him on this, saying that its not her fault that she resembles his friend. And Zoro, instead of properly processing this, just continues to yell and argue back.
Then when they run into her and Smoker again at Punk Hazard, the way he treats her has changed. He is now belittling her and treating her as inferior to himself. And while this isn't a uncommon way for Zoro to act to villains, Tashigi doesn't fit the MO of a villain. Hell, in Punk Hazard they are allies. And we haven't (to my recollection at least) seen Zoro treat allies this poorly in the past. Which leads me to think that the reason for this change is Zoro's way of attempting to separate Tashigi from Kuina in his mind.
It's safe to say that Zoro has put Kuina on some sort of pedestal. He was never able to best her in a fight, and (begrudgingly) viewed her as a better swordsman than him. Tashigi, while skilled, is not as good of a swordsman. So Zoro clings to that, focuses on that fact and reinforces it to himself by belittling her skills, insisting that he is the better, more skilled swordsman repeatedly. And while being a bit arrogant and cocky are definitely characteristics that Zoro has, the are very rarely if ever this badly unchecked.
I also think this plays into how he treated Monet in his fight with her. Part of it was him putting limitations on himself to prove his strength, but I also believe it can be read as him reassuring himself that Tashigi is actually nothing like Kuina. And the fact that he could defeat Monet with said limitations while Tashigi couldn't at her full strength just acts as further proof to their differences.
And while these moments between them are meant in part to be comedic, digging a bit deeper into them does provide insight into how Zoro poorly deals with complex emotions and how that leads to what could be considered his flaws as a character rearing their heads a bit more.
