I've got forms on my website populating Marketo leads through Zapier's "Create of Update Lead" action (data flow is website form -> Zapier webhook -> Marketo). This does not, however, create an association with the user's Munchkin cookie / anonymous lead data. Has anyone found a way to make this association happen without having to introduce additional API calls to associateLead? I would have thought that there would be a way to pass the Munchkin cookie to the action and have it associate with the lead, but can't figure out how to make this work.
Let's step back for a second. The best way to use a custom form and preserve all Marketo forms functionality (including automatic Munchkin session association) is to use a hidden Marketo form on your site. That's where you should be looking first.
If you really cannot go with Sanford's recommandation (which is really the preferred one), the other possibility is to capture Marketo cookie (mkt_trk) value and pass it with Zapier to a Marketo field then call the save2 endpoint from a Marketo webhook.