Namaskaram,

     Check this link for knowing the technique to auto fill field value from one field to another field based on the input of a field within the same module in Zoho CRM. For example, you may have two address fields as 'Temporary Address' and 'Permanent Address'. For some cases, the temporary and permanent address can be same. At that situation, you can auto fill the temporary address in permanent address by clicking the check box (Same as Temporary Address).  It will reduce the time duration while making the entry caused by re-entering the same information.