You can't configure DFS-R on a Multi-AZ or Single-AZ 2 file system

Microsoft Distributed File System Replication (DFS-R) is not supported on Multi-AZ and Single-AZ 2 file systems.

Multi-AZ file systems are configured for redundancy across multiple access zones natively. Use the Multi-AZ deployment type for high availability across multiple Availability Zones. For more information, see Availability and durability: Single-AZ and Multi-AZ file systems.