Billing customer with vendor invoice adding profit margin

Billing customer with vendor invoice adding profit margin

I have an invoice from a vendor for $300,000.   I wanted to add 10% margin say $30,000   and bill a customer $300,000 plus $30,000  = total  $330,000.       But I don't want the customer to see the margin %  nor the original vendor invoice.  

how can this scenario be reflected in Zoho Books?

Thanks!