Zack doesn't say anything, but that's probably worse than if he did. It usually doesn't mean anything good, when he goes unexpectedly quiet, even if he's pretending it's just because he's sizing up another door, this one on the side of a cobbled-together truck.

"Sure," he offers, eventually, maybe realizing that trailing off abruptly is both rude and suspicious. Or maybe just needing to fill the silence again. "That makes sense."