Make sure you check the SHA256 Checksum of downloaded file (particularly if downloaded from 3rd party site), against that published on the Zorin website.
You can verify whether the file has been downloaded correctly without corruption by verifying that its sha256 checksum matches the one listed after pressing the “View sha256 checksums” button on this page: Download - Zorin OS
To verify the checksum, we would recommend you to use an app called QuickHash, which can be downloaded from here: https://quickhash-gui.org/downloads/
After opening QuickHash, please navigate to the “Files” tab and select the “ sha256 ” Hashing Algorithm before clicking the “Select File” button to choose the Zorin OS .iso file and waiting for the checksum to be generated.
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Edit [2021-08-19] revised location of SHA256 checksums on Zorin OS website:-
