Zacharias returned the smile because it was the expected sort of thing to do. While he could be a bastard to most people, he seldom found a reason to be a bastard to her because they were in similar situations in regards to their families.
"My flat got overturned last week so I'm not half bad if anything needs to be fixed." He had Ginny Weasley to thanks for that. The woman beating him so beautifully, destroying his flat in the process and then Virgin Boy showing up to deliver the news that his father was dead. "But heading out to pick something up doesn't sound bad. We may have to make due with someplace muggle because the living inferi didn't leave this place in the best of shape."