Can I sync Steam ESO files with the Bethesda client so I don't have to download them again?

I downloaded ESO from a friend’s account on Steam to test whether or not it is playable on my computer. However, I intend to buy and download from the official website for various reasons. Is there any way I could avoid re-downloading the game files because they are over 80GB? Or is my only option to uninstall from Steam and re-download all over again?

Edit: clarification, I have it downloaded on Steam from a friends account, and want to play from the Bethesda client without redownloading if possible, not the other way around