I would like to create a function within CRM that allows my contacts to update the details I have entered.  i.e. to verify and correct those details. I have created a webform within zoho and have it visible on my website (wordpress) and a landing page but I don't know how to create the code so that when I email the contacts with a link to the form, they see their existing contact details and when they make changes and click save the CRM data is updated and stamped that the contact has verified their data.

How can I achieve this?  

Thanks in advance