The only thing that ZfcUser is really only concerned with basic account creation and authentication.
Your instinct to create a UserManagement module on your own is correct. ZfcUser only cares that some User entity exists, and that it implements ZfcUser\Entity\UserInterface. There's one built in (ZfcUser\Entity\User), or you can define your own User entity class (that implements UserInterface), and configure ZfcUser to use it (see the user_entity_class configuration key in ZfcUser).
Your UserManagement module doesn't need to know anything about registration or authentication. It's just a module for managing User entities. And User entities are just plain old entities, like any other. You can query them, update them, list them, paginate those lists, etc.