David,
No one has requested (or offered to develop) integration with Zapier. My brief review of Zapier sounds like you would want some sort of "trigger" event within the GlobalGiving api to "update" or trigger some other API - its like a middleware between API's. I could be completely off on this, since I did not read very deeply.
Since I am the Director of Engineering at GlobalGIving, if you want to take conversation offline, where you could detail your usecase on how you would use the GG API with a service like Zapier, I would be happy to listen and determine if it would be something to add to our product roadmap.
Warm regards,
Steve