Got a reply from Zillow support. Sounds like they don't offer app for Win phone anymore, but they are forwarding inquiries to the dev group to keep them apprised of interest.
thank you for reaching out to us. While we have mobile apps for both iOS and Android platforms, we currently do not have one available for Windows Phone. We are hoping to add our app to the Windows Phone repertoire in the future, but as of now, it is not offered for this platform. I always let our developers know when we get inquiries about Windows Phone apps, to show there is strong interest in this product. Hopefully we will add Windows Phone soon! Thank you for reaching out to us; have a Happy New Year!
Best Regards,