How can I pre-populate hidden fields in Typeform?

How can I pre-populate hidden fields in Typeform?

I am tyring to use hidden fields in Typeform to collect the contact's email address.

I tried using the Typeform extension for Zoho, but it is requiring that I ask for the fields I'm wanting to populate via the hidden fields. (Duh. I could do that, but that's not the point.)

Workflow:
  1. Send an email to the contact when a task is set to "in progress".
  2. The email asks the user to click on a Typeform link to collect branding information.
  3. These results will be imported (via CSV) into Zoho where the Contact's record will be updated with the new information from the form.
I need the email to populate the Typeform so that when I bring the data back to Zoho the email matches exactly as I have it.

The URL in Typeform is populating the email address,  but it does not populate/collect inside the results.