To implement SAP Build Work Zone, advanced edition in a multi-tier landscape, you need to create subscriptions in separate SAP BTP subaccounts. This is because SAP Build Work Zone, advanced edition is a subscription-based service that requires a dedicated subaccount for each tenant. You cannot create multiple subscriptions or service instances in the same subaccount, nor can you create multiple sites within a single subscription. Each subscription represents a separate site with its own content, configuration, and users. By creating subscriptions in separate subaccounts, you can align your SAP Build Work Zone landscape with your core business system landscape and enable content transport across different tiers.Reference:

Explaining the Planning Landscape for SAP Build Work Zone

Getting Started With SAP Build Work Zone