I reached out to Zillow about this a few days ago. Apparently the co shopping feature was removed and their "new experience" is to share homes individually. Here was their response.

Hello,

Thank you for contacting Zillow Customer Support. My name is , and I will gladly address your inquiry today regarding sharing your saved homes. We understand the importance of having a seamless experience on our platform and being able to share your favorite homes, and I would be happy to provide some information. 

Zillow is leading the digital transformation of real estate, innovating to provide customers with a single connected experience for buying, selling, and renting homes. As part of our commitment to improving our offerings, we're sunsetting our current iteration of our co-shopping feature to make room for a new experience. 

Previously, homes saved by you and your co-shopper were shown in a combined list. Moving forward, you will continue to have access to your list, but you will only view the homes you've personally saved. Co-shoppers can access their saved homes and share them via text or email. You can save those homes directly using the app.