Glad you found a solution in the end.
However, if you ever get tired of running into problems like these while trying to use Zapier to sync your Airtable and Webflow CMS, give PowerImporter a try. It puts all your Airtable data in your Webflow CMS, and then keeps them in sync automatically. Whether you add, update, or delete something in Airtable, PowerImporter will update the CMS accordingly, and it also takes care of all your multi-reference fields for you.
You could be up-and-running in 5 minutes and never have to worry about this automation again.
Disclaimer: I created PowerImporter, so forgive me for being a little “salesy”. 