Radeon driver lacks support for Vulkan but you do have Mesa, the open source implementation of Vulkan. This means that vkcube may still work or that some portions of Vulkan may be able to run.
We can double check with
lspci -k | grep -EA3 'VGA|3D'
Yes, you can install XFCE4 (and have, it seems) but one thing about Zorin OS Lite is that it uses a higher version of XFCE4 than the Ubuntu base does.
So, to achieve the same outcome, a user will need to use the staging repository for XFCE, rather than the Ubuntu Universe repository.
sudo add-apt-repository ppa:xubuntu-dev/staging
sudo apt update && sudo apt install xfce4