Wrote a blogpost about metric streaming in an environment with data diodes. This has been asked a few times in the forums with no real answer. Not claiming this is the full solution, but perhaps it's something to work with. If you have any feedback or suggestions, please feel free to leave a comment.
Zabbix with Data Diodes – Metric Streaming – Null Byte
Zabbix with Data Diodes – Metric Streaming – Null Byte