I explained it a little further down in the comment section.
You first look up "vol 20, no 4 p59-60". first thing you will find is Ex Oblivione by H. P. Lovecraft.
Then you only need to use the numbers on the back of the card as a cypher (paragraph-word-letter).

Can someone please explain how they solved Zakarion card? Even with the answer, I don't know how to solve it.

Thanks, it's cool to know the path you should have taken to solve it. Insomnia and Hypersomnia were particularly difficult for me compared to the rest

http://www.rosenbergclinic.com/id-112276/
this is the document you were given. it's on the rosenberg clinic website. I tried accessing the archive. password required. back to the document. googled all kinds of stuff, tried several numbers. at the end there's mention of the fateful year "Moberly and Joudain had their August visit to the gardens" -> googled "moberly jourdain august", got the year 1901. that's the password.
entered it. got a new document. read it. found astral in the document when trying around.

How did you discover the answer for hypersomnia? I found out the picture is the Flammarian Engraving, but having trouble figuring out any more links

you're very welcome :) so glad you like it

Thank you so much for this perfect guide

This one was fairly easy. You look up "vol 20 no 4 p59-60". You will find Ex Oblivione (the story the voice is reading to you) and then you use the numbers on the back of the card as a cypher (paragraph-word-letter).

On that one I didn't know what to do (as usual) so I took a screenshot of the pictures the game was showing me and used paint to cut out the picture with the train on it. I used google image reverse search and found out that it's a Union Pacific Steam Train. I did the same for the picture of the man and he is Cyrus K. Holliday, one of the founders of the township of Topeka, Kansas. He lived in the 19th century.
From here on I googled a lot. The hint with the Union Pacific was a bit misleading for me since it wasn't about that but only about railways in general. "Topeka railway 19th century" was the search that brought the right result. I found the wikipedia entry for "Atchison, Topeka and Santa Fe Railway" for which ATSF is an abbreviation.
Ahnayro isn't about being smart. I for sure am not smart. I'm just a very stubborn human being and I tried and failed a lot while playing this game and writing my guide.

Just generally stuff like this I am way to dumb for this game gg