Blah, blah, blah. Zack is just overly sensitive.

On the other hand he did get Zack to "smile" so there is that.

"You should try eating the dust of a world you've not destroyed," he suggests. "Your nature has been, as he said, changed. You are connected to worlds, but not in their destruction, but their life. By eating the dust of the dead you betray the life you should have."