If you would like to change the logo back to Zorin OS 6, follow the steps below.
1. Obtain the original Zorin OS 6 logo. If you have the original live DVD you used to install Zorin, boot the live DVD. Once you have Zorin running, open Nautilus (file manager) and navigate to the /usr/share/gnome-control-center/ui folder. Look for UbuntuLogo.pgn. Copy this to a flash drive. Maybe you have another computer with Zorin installed on it, you can copy the needed file this way too.
2. Go back to the computer that has the incorrect logo and insert the flash drive containing the correct UbuntuLogo.pgn file.
3. Open terminal and type sudo nautilus.
4. Navigate to the /usr/share/gnome-control-center/ui folder and copy the UbuntuLogo.pgn file from the flash drive to the hard drive. Make sure UbuntuLogo.pgn has the following permissions (see screenshot below). Right click file name > Properties > Permissions.
5. Check System Details again and the Zorin OS 6 logo is back!