[Zack doesn't quite laugh, but his attention turns down to the glass in his hands. He turns it this way and that, watching the liquid swish in each direction]

I would have probably driven you up a wall. [he pauses and seems to consider it, and this time he does laugh a little, a brief and quiet chuckle] No, I definitely would have.

[it isn't like he doesn't know why he earned the "puppy" nickname. He lifts the glass to take a sip] It wouldn't have been so bad, though, training under you.