I too can make keys for the Kawasakis and many other brands by the key code number.
Also from a picture of the key some times.
Have made keys to motorcycles using special tools as well.
I'm a locksmith.
The Z series Kawasaki codes do have two series in the computer; old and new.
Most of the key cuts (bittings) are the same in the old and new series, but some are different for the same Z number. Not sure when the switch over from old to new occured.
Best to email me if you want some information on cutting a key.
Rob
rstnick@hotmail.com