Vietnam form e mainland company tick third party invoice

Hello, our company will take a bill of lading to Vietnam Ho Chi Minh next week. The customer requires to apply for form e certificate. We are a Shenzhen mainland company(also registered in Hong Kong). Now we prepare bill of lading and customs clearance invoice to the customer. The consignor of the box list is made into Shenzhen company. The customer requires that the third party invoice be checked. Can you help me with this?(the agent we've been working with before told the mainland company that we can't check the third party invoice.).