Thank you for this detailed explanation!

I also came across this which was fascinating: ZoomInfo offers a free product that you have to connect with your email. Once you do, they scrape EVERY single contact in your email to enrich their database.

So, technically, it is YOU who has signed over your entire contact list data to ZoomInfo and agreed to their Terms and Conditions which states that they can now sell YOUR DATA (your email and everyone else's in your contact list)

https://www.vice.com/en/article/y3zqbw/zoominfo-privacy-laws