The link to Z-Library itself is one of the legitimate ones from what I know so I wouldn’t worry on that side too much.
PDFs have a few exploits that could infect a system. However they are rare and not efficient especially if the intent is to infect as much machines as possible.
If you don’t have much technical knowledge to analyze the files yourself, I would recommend you open the PDFs in Virtual Machines without any acess to the internet or opening the files only when you have disconected your device from any acess to the internet.
Tools like the one mentionned by someone else in the comments would be good to prevent from having to worry about a potentially malicious PDF. Various tools are around to convert a malicious file lile PDFs into regular “trusted” PDFs (said tools flattens everything making it impossible to select text or click any URIs included). I would look up the trustworthiness of some of those tools first (to not try and avoid malwares by installing one).
That was way too long of a comment but I hope it could ease some of your worries.
In the rare case where you are actually not a troll, let me put it simply.
Your previous post was blocked for the behaviors of certain individuals in the comments, including you and the topic itself which was as good as spouting: “Why not use Google drive for sharing media? It’s free and there is way less hassle than what all of you have been doing for decades. I am right you are wrong.” .
Is it possible that plenty of people are wrong and have been doing things wrong for a long time? Yes, it is possible. In this case, bring good arguments, show proof, and debate. Do not bring baseless beliefs into an argument and say you are right about it.