Zorin do love black screen. I had face black screen during shut down, restart and suspend. Although old kernels have fixed the issue but it's a nightmare now. I now when I put my password on login screen the screen gets black and nothing comes.
This started happening when I reduced the resolution quality in settings.
I can't set them back since after I login black screen appears nothing I can do after that except trying ctrl+alt and some function key which brings me back to login screen
This will get you to a terminal. You can use xrandr to set the resolution
xrandr
Grab the Monitor Identifier. It may be VGA-1 or HDMI-1 or DP-1... In this example I will use DP-1. Replace that with your actual identifier. Replace the resolution with the last known working res.
Instead of xrandr and see if that works?
If it doesn't... (Your profile lists that you are using both Lite and Core...) In Zorin OS Core (gnome) the configuration file should be ~/.config/monitors.xml
In Zorin OS Lite (XFCE), it is ~/.config/xfce4/xfconf/xfce-perchannel-xml/displays.xml
If you are unsure, you can check with the command sudo find . -type f -name "*displays*"
You can use the mv command to rename them to a Back-up, allowing the system to set a Default Configuration.
For Zorin OS Lite: