We have a problem with duplicates. So we create a lead on Zoho whilst prospecting. Once the customer is happy to proceed we forward them to a webform powered by Zoho on our website.

We need them to fill this form in because it involves them accepting terms and conditions.

The form is at a fixed link which we give out i.e. www.company.com/form

When this lead enters Zoho it creates a duplicate and the sales guy just don't use the merge and find duplicate functions at that point. So ideally it needs to be automated. 

I don't want to use a custom URL for each client as its much easier to give the same URL to all. 

But I want Zoho to either automatically merge the leads when created OR go through an approval like process where Zoho prompts us to say it may be a duplicate and guides through the merging process then.