Zorin takes a long time to boot

It is like.. the login screen comes in line 3-5 seconds, after I put my password and press enter, a black screen with a cursor for 20 seconds comes and then the desktop loads

Have you checked your autostart programs to see if anything is set to autostart that you do not need?
You can easily look in ~/.config/autostart (I have three items in mine) or in Settings > autostart

There is only 1 item.. canberra-gtk-play.desktop

Out of curiosity, I tried pressing CTRL+ALT+D on boot just now and not much was displayed only a big "Z".
Then tried after login. Just normal black screen until session started.
No big deal. I may try it again sometime.