They charge for bandwidth, server cycles and rent.

So they don’t profit?

I find it interesting that zlib is supposed to be compensated for their servers but the authors aren't supposed to be compensated for their writings.

Personally, I'm in support of zlib / libgen / other illegalist libraries. But it is kind of funny to see where the morality lies on this.

Your argument is skewed.

Z-Library guys didn't extradite any site users who didn't pay for their servers and handed them effective life sentences.