Whether zero-rated tax invoices and purchase confirmations can be issued when receiving a down payment

When supplying goods to an overseas corporation, I have previously issued zero-rated tax invoices to the client's domestic entity at the FOB point and requested/received a purchase confirmation. This time, due to the large scale of the contract, I intend to proceed after receiving a down payment, but the client's domestic entity is requesting that I issue a tax invoice. In this case, I would like to inquire whether it is permissible to issue it at a zero rate and if a purchase confirmation can still be obtained.