Business to Business + Enterprise Identity Scenarios
This is essentially a hybrid between B2B and B2E for larger SAAS applications (such as Zendesk). In a situation like this, users would primarily be grouped into companies, but you may also have internal users (employees) who log into perform support or administrative tasks. Those internal users will typically use federated identity to authenticate.
The following is a list of articles on this website which will help you to implement this scenario: