It can help you locate cards.
You'll be able to separate red and black cards even though your spectator shuffled the deck!
It can even help you put the shuffled cards into any order you want.
Importantly, Z DECK can be handled by a spectator and can withstand some scrutiny without exposing the secret.
When you own it, you will find that it can do many, many routines.
It's going to be your new gimmicked deck that you're going to use a lot!