Personally, I don't think Zono is really being petty. He disagrees with Miyuki. Again in his eyes, it seems like he hurt a teammate and he can't just overlook that. I think the main thing is they have a different viewpoints on what is right and wrong and are clashing on it. They're both strong personalities. I do agree that Zono should try to help more, but in his eyes, he just has big expectations from Miyuki and is too focused on that.