In Odoo we can do this by enabling the standard "pedimentos"  flow with automatic inventory value and using FIFO or AVCO for this purpose.

We add the pedimento using the landed costs feature with the correct l10n_mx modules for extended functions and pedimento and the field to add it to a stock move should be added, this can be further explained in the public mexican localization documents.

https://www.odoo.com/documentation/15.0/applications/finance/accounting/fiscal_localizations/localizations/mexico.html

The interesting part for this is how we sell it, in order to sell multiple at once we will need the manufacturing app and create an invoicing product that should have a BoM created as a kit, this kit is going to contain the components that have the pedimentos.

On the BoM creation, we add the two products that have the "pedimentos" as materials for the kit.

Then we just have to deliver the finished product, validate and then create an invoice (ORDER IS IMPORTANT)

Once we create the invoice, all the customs number from all the products inside will be added into the invoiced line.

Once this is done we can see that the PDF for the invoice has all the numbers and these come from just one line :)

The cool part about this is that we can use standard functions and it is AUTOMATIC :) Have a good day.