POST invoice vs. CRM ID

Hi,

we're using Zoho CRM synched with Zoho Books.

Now I want to do a simple POST call to create an invoice.

First i tried to use the account id from zoho crm as the customer_id in the POST call, but it works only for a few customers. For the others I get an error message that there is no account statement under this id.

My problem is, that i have to use the crm account id for different reasons, but also because this id is in our internal billing system linked to the invoice that we are about to POST into zoho books.

This is how my api call looks like: (reduced)

POST https://www.zohoapis.eu/books/v3/invoices?organization_id=xxx

{ 
        "date": "2024-05-31",  
        "customer_id": "334239000002927687", //zoho crm account id
        "zcrm_potential_id": "334299000012228049",
          "custom_fields": [
        {
            "subject": "test subject"
        }
    ],
             
        "currency_id": "181762000000000071",
        "currency_code": "EUR",
        "currency_symbol": "€",
        "currency_name_formatted": "EUR- Euro",
          "line_items": [
            {
                "description": "product a",
                "quantity": 1.00,
                "rate": 1.00,
                "item_total": 1.00
            }
        ],
        "total": 1.19,
        "template_id": "181762000000000102",
        "template_name": "Standard Template",
        "template_type": "standard",
        "can_send_in_mail": false
        }