I’m having the same issue. Did you manage to find a solution?
I contacted Zapier support and they were very helpful, but I’m no closer to solving this. I was trying to use a webhook to send a PATCH request using the Webflow API as I thought that might solve the problem. But apparently the Zapier webhooks app doesn’t currently support the sending over of an array of line items (which is how the photo URLs are formatted from Airtable in my case). There is a feature request to update this but no ETA.
They suggested using a loop in the Zap but this also doesn’t work since sending one photo at a time in the webhook just overwrites the image each time.