Backing up Drive with a Secure Zone / I am confused

I recently decided to create a secure zone on my new C: Drive since it had a lot of free space. I then thought I would backup some of my photos(stored on separate drive E:) in the Secure zone on drive C: as a secondary backup location.

I thought I understood that the secure zone is a separate partition, but when I decide to do a backup image of my C: Drive, I cannot exclude the Secure Zone from the backup. I thought it was a separate partition. Why can't I exclude the SZ if it is a separate partition?