Hi, I have an online portal to sell some digital assets. The portal is completely independent and has no integration with Zoho in any way. 

Now I am planning to use Zoho Invoice API to invoice my users. which means whenever someone buys anything from my site. I will hit ZOHO invoice API and generate an invoice for that particular customer.

But according to invoice API documentation, customer_id is a mandatory field to create an Invoice. 

So I am planning to create a customer in ZOHO if it does not exist, using the API only. then pass the customer_id to the invoice API to generate an invoice.

The problem is, I am unable to find a relevant API which I cant hit to create and get customer_id before hitting the invoice API.