Zillow sends a rental lead to TextWork. If the lead has a phone number, TextWork texts them and runs the script you picked.
Activate it in Company Settings, under Integrations. TextWork shows a webhook URL and a security token. Email both to Zillow so they can deliver leads.
A lead with no phone number is saved, and nobody is texted. The same lead arriving twice is skipped.
How to use it is in the Zillow setup guide.