Transfer of Parameters from a non-zoho URL to a Page or form

Transfer of Parameters from a non-zoho URL to a Page or form

Hello,

I am trying to find out how to transfer URL parameters from a URL based on mydomain to a Zoho Form
embeded on an HTML page

Example:

URL based on Mydomain.com with parameters (mostly just a clientID)
This would point to a HTML page with an embedded ZOHO form (iframe1) and embedded ZOHO Page (iframe2)

STEP1
The objective is to have the ClientID parameter, transferred to iframe1  and prepopulate the clientID field in the form in iframe 1   - So that the user can fill in other fields including upload of a video and have all that linked to his clientID

STEP2
I want then to have the uploaded video in iframe1 to play in iframe2 - i.e the client ID parameter is then transferred to iframe2 where a Zoho Page is embeded

Can someone suggest a way to do that with sample HTML snippets

Also:
The initial URL would appear as from my company and not based a Zoho based URL - which one of the key criteria -  is there a requirement to use a custom domain for the a customer portal. This is not ideal because I don't want to put a login screen to this.

Thanks!!!

Joseph