Maybe unrelated, but i was having the same problem just a week ago. Zorin won't shutdown, no matter what. Been trying everything i could find, like turning off suspend, setting power button to poweroff, using 'poweroff -p' command, editing GRUB, but to no avail. Even livebooting Zorin 16 Lite failed to power off my laptop.
Turns out, for me, it was something to do with the latest Linux kernel. It was upgraded from 5.11.0-40-generic to 5.11.0-41-generic a week ago. Booting with 'Advanced options for Zorin' and selecting 5.11.0-40-generic kernel does the magic and managed to shutdown the laptop for good. Now i'm defaulting to boot with 5.11.0-40-generic kernel with Grub Customizer.
My laptop use AMD A4-9125 processor, might have something to do with that probably?