To be honest, I didn't measure it on my system before. Recently I had sold my old PC and got myself older system in that place. I know it was working properly. I noticed that I have slower speed when I was downloading torrents and youtube started to lag. Then I measured and find out that I have indeed slower speed.
Again, silly of me, I didn't try it previously since I was sure it was issue on computer side, but now I disconnected my internet switch and connected PC straight to router and speed is back to normal.
For now I am going to mark this as solved and going to try to fiddle with my router and switch. Turns out it's not really Zorin issue (at least on surface level). I am not really IT guy, so I'm not sure how deep I can go. If anyone has any suggestions to find if there is link between my issue and Zorin OS, I'm all ears.