Zoho's Account Level Organisation Structure and Classifcation
Zoho’s suite of services can be classified into two types:
Organisation Bounded Apps (All the app account services will Come under single Parent Organisation).
Non Organisation Bounded Apps (Each service's organisation are individual Child Organisations).
The following Zoho services are considered Organisation Bounded Apps:
Zoho One
Zoho Directory
Zoho Cliq
Zoho Mail
Zoho Connect
Zoho Forms
Zoho Vault
These services provide foundational capabilities that support organisation level management.
All Other Zoho Services(Like Zoho CRM, Zoho Desk etc.,) are Non Org Bounded Apps. Each service's organisation are individual Child Organisations.
Here is the Visual representation of the Structure:

So, How & When a Parent organisation will get created?
When the first user of an organisation creates any of the Organisation Bounded Apps(listed above), a separate data space called 'Parent Organisation' (or) 'Zoho Organisation' will be created on Zoho servers. This user will become an admin/owner for the particular Parent Org, and can invite employees from their company within the particular App Account to register with Zoho to become members of the particular parent organisation.
The admin of the particular organisation will have the privileges mentioned here.
How do I find out which organisation I'm part of?
Sign in at accounts.zoho.com.
Click Settings in the left menu, then scroll down to the bottom of the page.
You can view the name of your organisation, and the contact email address of your Org administrator. If you are not an organisation user, you will not be shown this information.
Can i be a part of two different organisations?
An user can be a part of only one Zoho Organisation. However, there may be scenarios where users will need to access the applications of an another organisation as well. In those cases, they can join the other Org as an External user and access its apps, but it comes with certain restrictions on access privileges. External users of an organisation refer to users who are actually part of another organisation, but are only present in this organisation to perform specific functions. They will have limited roles and restricted access in the organisation they are present as external users. To learn more about External users, refer here. Deactivate/Deletion of users:
In Non Bounded Apps
User deactivation and deletion can be managed at the instance level. The UI controls for these actions are available within each app.
The option to deactivate/delete users from a specific instance will be available in the respective app's settings.
Users deactivated or deleted from an instance will still be able to access other instances of that app and also create new ones.
They will also retain access to other Zoho apps.
In Bounded Apps
Since Bounded apps are tied to a single organisation, there are some differences from Non Bounded app's behaviour and limitations when it comes to deleting users.
Deactivating an user from a Bounded app:
This can be done from the respective app's settings.
User's app data remains intact and can be reactivated when needed.
The user will still be able to access other Zoho apps.
However, they cannot sign up for the same app themselves using the same account.
Deleting an user from a Bounded app:
The user's mailbox will be deleted, but will still be able to access other Zoho apps in the organisation.
For other bounded apps, users cannot be deleted individually in apps. They can only be deleted entirely from the organisation along with closing their Zoho account.
Article Created by Maddy | Zoho Partner Support