Hey Alan,
Sounds like you need to add a step in your Integromat to get the collection details from 2 collections, and send both back to Zapier.
And regarding your question about forms, yep their certainly is - https://discourse.webflow.com/t/how-to-add-hidden-form-fields-to-forms/1966
I use this hack quite a lot to send important details ‘along for the ride’ on Webflow forms. For example, I send ClientID & Client Name along with pretty much every form.
The way I always structure my Webflow pages is that most of my forms are located on a Collection Item page, which is the unique ‘dashboard’ or ‘interface’ for a single user. For example, Joe Bloggs would have a Collection Item page /joebloggs. I do this because it allows me to send CMS content from Joe Bloggs along for the ride on forms, like his ClientID and Client Name for example.
Another way to do it is by using MemberStack (if you’re using it), and use the Custom Attribute feature which allows you to send along any info that MemberStack has on that client/user. You can assign additional text fields in MemberStack, so you could put a ClientID in there too.