Zone transfer is on our roadmap however not planned for CY 2019.
-Rohin KSethuraman A commented
We will consider using Azure DNS as the primary and have another provider as backup.
- Do you require zone transfers in to Azure DNS, or zone transfers out? Why?
Both. Initially we would start using Azure DNS as a backup and later we would want to migrate that backup to become the primary.
- Do you require AXFR or IXFR?
It depends on the other providers, so at this point I think support for both makes sense.
- How should zone transfers be secured?