Yes there are a lot of really good track day/evening sessions throughout the year at Knockhill.
The Track Scotland and SIDC events are usually very good as well as most of the "corporate" "private" events.
Also you will find on a weekly basis Knockhills' own events are usually very enjoyable, but only the open pit sessions.
I am afraid you will have a problem getting the numbers for a purely Zed track day, however if you mix it up a bit with other marques than it may work for you.