At the bottom of this documentation page:

It says the following:

File Upload

While uploading a file to the Dialogflow bot, a text message that says File Uploaded Successfully will be sent to Dialogflow. No text will be displayed in the chat window and the text will not be sent based on the language. The user needs to handle the file upload intent based on the text response."

I checked the History inside my Dialogflow console, and I did not get any text message "File Uploaded Successfully" as you mention in the documentation. So there is no way to handle file uploads in the Zobot Dialogflow integration right now. 

Also, in the tutorial video you made on this topic, it looks as if the message is supposed to appear in the chat window, but the documentation says that doesn't happen (underlined).

Can you please look into this issue?