Currently the method isValid of ZPersistentObject accepts either a ZString or a ZReference as the value for Z2K1. This is because for a while we had a bit of a mess while transitioning from Z9 to Z6, but currently all Z2K1 should already be Z6s.
- Change isValid method so that it stops allowing Z9 as a valid value for the ID
- Make sure that tests pass
- Try to manually create a new ZObject from the Vue interface to make sure that we are not breaking things and the front-end is creating correct ZObjects.
- (If not working), fix front-end to send Z6s instead of Z9s as the value for Z2K1.