Note that LibGen is now a subset of Z-Library, as whilst ZLib sourced LibGen to seed itself, it's not contributed its own acquisitions back to Library Genesis.

The Pirate Library Mirror (your second link) is a complete archive of Z-Library, though it's a bulk archive of several TB and not readily accessed for individual titles. The PLM is intended as a tool for building archives rather than as a direct source itself.

(The pilimi.org link itself explains much of this.)