No it's not. Well it started out that way, but libgen is 7TB, zlibrary added another 16TB to that, which was not shared in the way libgen is.
The core of Libgen is indeed 33TB. No idea where you get your 7TB from. The content difference between it and zlibrary is marginal from what I understand.
Including fiction (but excluding the scihub mirror, and comics), Libgen is actually about ~60TB. Z-Library mirrors this, and adds about ~24TB exclusive to them.
Maybe 80% of it is. Zlibrary, rather greedily, accepts its own individual uploads and does not mirror them to libgen anymore. Probably due to their monetization policies.