If I got a black screen at boot, and never saw the OS, I would simply hold the shift key at boot and then revert to an earlier kernel that worked. But Aravisian gave you more specific instructions that you should do first and see how it goes.
I tapped the L. Shift key but no boot options appeared. Was I doing something wrong?
As you maybe know, I use Zorin OS as my main OS, it's not installed alongside any other. Does it matter?
Sadly, all I can do is reference here:
Sometimes, getting at it is Tricky.