Zapier is both wonderful and frustrating.
It provides such power, but at the same time, doesn't let you get QUITE deep enough into the guts when you really know what you're doing.
For example: I have one source that's giving me multiple options for a custom field that goes into another application. The "update record" for this second application doesn't seem to have a way to say "I'm giving you multiple values". Using "line items" seems to break, using comma-separated text seems to break...
But there's a handy "logs" (beta)! But it doesn't exist on test runs, only on live runs. Boo.