Who said that Zlib is gone? Besides Tor, you can get access to personal domains by sending an email to blackbox [at] zlib [dot] se
I know it may sound scammy, but if you still have a Reddit account I’d go to r/zlibrary and browse the pinned megathread for more info. I really hope that this community will eventually migrate here though…
Privacy versus convenience… For what I know, the most common solution to your concern would be to setup a Calibre server and access it via your Android devices. But that’s obviously a tad more complex than uploading EPUBs to Google Books.