Although the "(tested)" implies something, it is misleading. Essentially, they are the exact same driver, however the tested one includes instabilities - it should say Testing, not Tested.
The 535, 545, 550 or 555 drivers should all work on that card.
This does not sound like a driver issue exactly. It may be a module issue.
You msut fully remove and purge the driver as outlined by @Storm but you may take the additional step of reinstalling your kernel. Let's be thorough:
sudo apt-get install --reinstall linux-image-$(uname -r) linux-headers-$(uname -r)
Do Not Use the 6.8 kernel, for now. Instead, set your boot default to the 6.5 kernel, if you need:
Once that completes, install the Nvidia Driver:
sudo apt install nvidia-driver-535
Once that completes with no errors, reboot But do not enter the desktop, yet. Instead, before logging in, ensure that you are set to Zorin Desktop on X not to Zorin Desktop on Wayland.
Then login in and test.