Not sure that will work. Bubble expects the data in a very specific format, and it doesn’t appear Zoho sends it in the way Bubble expects (which is in JSON format with the content of the file base64 encoded).
That’s not to say a solution couldn’t be developed - perhaps using a proxy endpoint - but unless I missed something in my cursory look at the Zoho docs, I don’t’ think you can specify a Bubble endpoint directly via the Zoho save_url parameter.
I’ve battled Zoho CRM’s APIs and while is not Zoho Docs it might be useful nonetheless.
The best way I found to manipulate and interact with my Zoho data was by building my own APIs with Zoho. I’m not sure Zoho Docs has that functionality, though. You could test it out using Zoho Flow. It might have some pre-built Zoho Docs integrations or you can write your own scripts using their Deluge language.