UPDATE:
I have experimented quite a bit with this - and I have found, that the approach described above does not really work.
I have found, that the following works best (for me):
1. When inserting the Z in the case: insert the top plastic clip (next to headphone) first, the bottom (wide plastic, leather covered) last.
2. When taking case off: remove the bottom first, and the top plastic clip last. ( It may be easier to remove the bottom if you open the Z )
It is somewhat tight, but overall very simple...