I have an RTX 5060 GPU and I struggled to get Zorin 18 installed. After a day of trial and error I think I have a working solution for anyone with a newer nVidia GPU.
Note (I'm going from memory so verbiage may not be exact.)
When installing Zorin 18 use Install Zorin (Safe Graphics). Do your install and reboot. Once you're to the login screen click your username and then in the bottom right corner is a gear where you can change between Weyland (Zorin Desktop) and X11 (Zorin X11) and select the X11 version.
Once in Zorin do a Software Update either via the GUI (Software Updater) or the terminal using sudo apt update && sudo apt upgrade.
Reboot. (I don't know if this is necessary, but there's a firmware update so it doesn't hurt.)
Once back in Zorin go to Software & Updates and click the Additional Drivers tab. Choose Using NVIDIA driver (open kernel) metapackage from nvidia-driver-580-open (proprietary, test). Let it install and then click the Restart button.
Once you're at the login screen click your name, and then click the gear at the bottom right again. It has probably changed to the Weyland version. Select the other one (I think it was Zorin Desktop this time) which will give you the X11 version.
That seems to be the proper way to get modern nVidia cards working.
I strongly advise trying to update the Linux Kernel using the Mainline app. I tried versions 6.15, 6.16, and 6.17 and all caused issues with the nVidia driver. It wouldn't let me install them, even if I rolled back to kernel version 6.14. Maybe I was doing something wrong, but I don't think so. Something wasn't playing nice with the newer kernels.
Hope this helps other frustrated nVidia users.