Hi Massimo,
To achieve what you described, you must specify in each invoice which house bank need to process that payment.
Next,FBZP- Bank determination, make sure the payment method in the invoice match the payment method specified for the house bank (Ranking order & bank accounts).
I would suggest you to pick up few invoices for each house bank and try what is explained above. Then, once you are successful, then you can process more payment.
Like Mukthar said you can specify payment method in vendor master data, if you have only one type of payment method, otherwise ignore that step.
Regards,
Sam