Backing up your ZenCart files in cPanel
Login to your cPanel control panel. Scroll down a ways until you see the Files box.
Click on Backup Wizard in the Files box.
The following screen will appear:
Click on the button labeled Backup –>.
The following screen will now appear:
Under “Select Partial Backup” select Home Directory –>
NOTE: I prefer to use phpMyAdmin to backup my database files. You can opt to select Full Backup à to use the wizard to backup both you files and database.
Once the page loads, click on the Home Directory button to download your backup:
Once clicked, a small box will open:
Choose “Save File” and then click on OK.
Your files have now been saved to your computer.
IMPORTANT: Unlike .zip files, Windows has no built-in support for tar archives or gz compressed files. In order to open a tar.gz file you will need to use another application.
Here are some recommendations:
If you run into any troubles, just let me know below. 
Related tutorials that might interest you:
May I ask why you prefer to use phpMyAdmin to back up database files? Thanks!
For me, using phpMyAdmin is easier. It’s how I first learned to make database backups. Plus you can specify which databases to backup, as opposed to the wizard.