iPhone Export 3rd party epub from iBooks to computer

[Lastrovib]

Previously, I have imported an epub file to Books. (not bought from Apple Store, no DRM)

I wish to export the epub from Books to my PC, but I find no way to do so.

The epub file does not show up in iTunes or iMazing (a 3rd party software) when I connect my iPhone to my PC.

I tried disabling iCloud Drive but the epub disappears from Books once iCloud Drive is disabled despite me downloading it to the phone before disabling.

Any help is appreciated