in Windows you double-click on the downloaded file with your mouse to start installation. Not sure for MAC. if this doesn't work you will either need to contact support or delete the original download and try again. did you buy it from an authorized seller?
What is the full file name? Is it a zip file? It should not be a zip. Can you just take the zip off the end of the file? Did you use Microsoft Edge to download it? Try using a different browser to download it.
TurboTax minimum system requirements for Windows - https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-...
TurboTax minimum system requirements for Mac - https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-...
Find download using Windows - https://ttlc.intuit.com/community/installing/help/find-your-turbotax-for-windows-software-download/0...
Install TurboTax for Windows - https://ttlc.intuit.com/community/refund-status/help/how-do-i-install-the-turbotax-software-for-wind...
Find download using Mac - https://ttlc.intuit.com/community/installing/help/find-your-turbotax-for-mac-software-download/01/25...
Install TurboTax for Mac - https://ttlc.intuit.com/community/installing/help/how-do-i-install-the-turbotax-software-for-mac/01/...
TurboTax files don't download as zip files. Are you downloading/saving to your C drive? TurboTax requires that.
Can you remove the .zip extension, then double-click? Or right-click, and Extract?
You can Contact TurboTax Support for more help.