"There's a lot you don't know," Harry said with a shrug. "There's a lot that almost nobody knows. I don't know if it'd make you feel any better to know about it. I don't know if I want to tell you."
He didn't owe it to Zach to explain any of it. In the end, it didn't really matter. He didn't want to be known for the things he had done, or the things he hadn't done, but he wouldn't have a choice in how the rest of the world viewed him or how he went down in the history books for his part in this. All he could do was try to ensure that he was living in a world that viewed it as a good thing that Voldemort was dead, a world where people weren't living under a potion or on the run, where people weren't living in fear. Maybe it wasn't his responsibility anymore, but he still wanted to be a part of it.
He stopped outside the cafe, hand on the door knob, as he thought about Cedric. "Yeah," he said, imagining Cedric as a part of the DA. "I think he would have." If he'd had the chance, of course. But that wasn't the point, he'd wanted to understand Smith's motivations. Which he did, now. Better than he had before, at least.
They were very selfish motivations, from where Harry was standing. Meanwhile, Harry had done everything in his power to put the bigger picture, the good of the wizarding world, before his own emotions and even his own life. He had his selfish moments too; everyone did. But he wondered if Zach would have cared a single whit about the war, the dead people, if he hadn't known any of them. He didn't think he wanted to know the answer to that question.