2 businesses = 2 Zoho CRM accounts? Can we use 1 Zoho Invoice account?

2 businesses = 2 Zoho CRM accounts? Can we use 1 Zoho Invoice account?

My husband and I are both self-employed (two separate businesses, no employees other than ourselves) and currently have two separate Zoho CRM (Professional) accounts. We were falsely under the impression that these accounts would offer free access to Zoho Invoice. 

I now realise that the "free invoicing" refers to the Invoicing feature that is part of CRM but this is not suitable for our requirements as we need various invoicing templates. However, purchasing 2 separate Zoho Invoice accounts in addition to the CRM accounts is making this whole exercise very costly on an annual basis. Is it possible to use just one Zoho Invoice account and manage the two separate businesses as separate "organisations"? Or would that mean two separate payments regardless? We both only have small sole-trader businesses with less than 50 customers each, so all this subscription duplication seems a bit of an overkill and very costly.

Thank you for your advice.