The DCs in Azure are grouped based upon the Azure regions they reside in.
The DCs in the South Central US region (aka ZSC DCs) will support authentication and authorization for domain-joined devices connected to the Virtual WAN in the same region. The ZSC DCs will be in the Austin-ZSC site and will use InCommon certificates The ZSC DCs will be deployed in early-to-mid 2023.
The DCs in the West US 2 region (aka the ZW2 DCs) provide BC/DR for the Austin Active Directory and Azure Active Directory. The ZW2 DCs are in the Austin-ZW2 site and use InCommon certificates. The ZW2 DCs will be replaced by DCs in the North Central US region when Availability Zones become available in that region.