Recently built a new home & want to add to Zillow so we can import/track value in Mint.

Use the "make me move" feature from your user profile (click your user name or avatar to get to your profile page; use the "listings" link in the left column to get to the page where you can create the "make me move".

Once you have created the "make me move", you have a home details page for the property.  Then, if you don't want the "make me move" you can remove that, and the home details page will remain.

Whether Zillow will actually have the county records data is not clear.  The local data provider companies are supposed to provide data on all "ownership residential units", so it should show up eventually anyway.

I added an "empty lot", and Zillow already had the county records data on the lot size.

Zillow files everything by street address, and leaves the address the same even when the county changes it for new construction...  This could be an issue with finding a property that has new construction.  It may have the old address.