Some users rename the extension to .epub or .cbz if the internal structure supports it.

: Use the Files app on iOS or Android to extract the contents. Read the book :

The file "AnnaXXX.zip" likely refers to a compressed archive from Anna’s Archive, a shadow library that indices books and academic papers. On this platform, .zip files are typically used for specific collections or when the source material (like HathiTrust) consists of many individual text or image pages. Security and Safety