I removed the OBCZ flag and added a "closed" remark. However, you could and should have done that yourself.
The zone should neither be removed nor reused or renamed, because books that have been released there and moved on, really have been released there. It's a part of their journey and their history. If the crossing zone would be removed, all "old" books would lose this part of their history as well.
Please catch the remaining books (only those which are moved to another location by you) yourself and make new release notes for their new location.