To setup Zillow Estimate follow the below steps:

Step1: Create a page with Zillow Estimate template:

Step2: Get the API Key

The widget works based on Zillow API. Results are returned from Zillow.

Go to this URL to take you Zillow API Key – https://www.zillow.com/webservice/Registration.htm

Step3: Add the API key in Theme options > Social & Contact > Social Accounts

Step3:  Go  Appearance > Widgets and add the Zillow Widget to any sidebar.