Implementing Azure AD cross-tenant synchronization. The feature makes it really easy to implement the technical part of synchronization between different Azure AD tenants.
To use this feature, both the source tenant and the target tenant require at least a P1 Azure AD license. The administrator and the application used to implement the feature needs to have the delegated authorization.
https://www.microsoft.com/en/security/business/identity-access/azure-active-directory-pricing