emailSendTo = List();
emailSendTo.add(customer_email);
sendInvoiceParam = Map();
sendInvoiceParam.put("to_mail_ids",emailSendTo);

response = invokeurl
[
  url :"https://www.zohoapis.com/books/v3/estimates/" + quote_id + "/email?organization_id=" + org
  type :POST
  parameters:sendInvoiceParam.toString()
  connection:"zoho_apps_connection"