multi availability zones for ebs volume

Hi, AWS EFS is a possible alternative to EBS for you. It offers cross-region replication. See https://docs.aws.amazon.com/efs/latest/ug/efs-replication.html

You can use Amazon EFS replication to create a replica of your Amazon EFS file system 
in the AWS Region of your preference. When you enable replication on an EFS file system, 
Amazon EFS automatically and transparently replicates the data and metadata on the 
source file system to a new destination EFS file system.

...

Amazon EFS automatically keeps the source and destination file systems synchronized. 
Amazon EFS replication is continual and designed to provide a recovery point objective (RPO) 
and a recovery time objective (RTO) of minutes. These features should assist you in meeting 
your compliance and business continuity goals.

If multi-AZ block storage is required, then iSCSI volumes presented from a multi-AZ deployment of Amazon FSx for NetApp ONTAP is a good solution.