expression: know your zs?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hello,

When I watched the criminal minds 1x01 episode, the guy (unsub) said to the girl (victim) while he tries to sell a car to her.

“You know your Zs. I’m impressed.”

I think it means maybe she knows a lot about car like, a to z. I guess this in the context but I’m not sure. What do you think?

Thanks,
sweetpumpkin

2

According to the script at: scribd.com/doc/23408766/CRIMINAL-MINDS-s101 , the car is “a red Datsun Z”. So, I guess he’s just saying that she knows a lot about this model of car.