Issuance procedures for Local L/C (Purchase Confirmation) and Zero-Rated Tax Invoices in export structures via direct purchase platforms

I have an inquiry regarding the issuance of Purchase Confirmations (Local L/C), Export Declarations, and Zero-Rated Tax Invoices. The transaction structure is as follows: Company A (an outlet supplying domestic goods), Company B (our company, a trading company that purchases goods from A and supplies them to overseas direct purchase platform C), and Company C (an overseas direct purchase platform with a domestic branch that delivers goods purchased from B to the final overseas consumer). Since our company (B) can only generate operating profit if we receive VAT refunds, we must issue zero-rated tax invoices. However, because we are not exporting directly to the final consumer, I am confused about the correct procedure. My current understanding is that if Company C issues an Export Declaration, we (B) use that as the basis to issue a Purchase Confirmation to Company A, and then Company A issues a zero-rated tax invoice to us based on that document. I am writing to confirm if this understanding is correct. Additionally, if Company C does not issue an Export Declaration, I would like to inquire about what route or method we should use to obtain a Purchase Confirmation (currently, we only have access to the customs clearance list for the exported goods).