Can this be done I do not want to retain the Chrome O.S.
Yes, it can be done using Crouton:
I admit I know nothing about Chromebooks. But if Chrome OS is just another flavour of Linux, and you don't wish to keep it, I would go to Zorin OS download page, scroll to the bottom to "Getting Started" and print out the instructions. You should be able to install Zorin Lite 15.3 to replace Chrome OS. I use Balena Etcher myself, but the instructions miss out one step = when you click on the .iso file in downloads, you have to "Extract", then you have a new file in downloads to use.