Hi,
How do I uninstall Debian (Gnome) and install Zorin or Mint? Thanks!
You don’t really “uninstall”. Make a bootable USB drive from the ISO of your new distro (Mint or Zorin), boot from that into the installer, and choose whatever install option says “use the whole drive” or similar.
And if you have any data you want to keep from your current distro, then back that up before you do anything. I never do any work with my Linux machine (I use my Mac for business) so I just wipe the entire thing and start over. But a lot of people here have Linux for work and / or personal business, so if you’re one of those then think real carefully and make sure you save those files to another USB drive before you begin installing a new Linux distro.