So it looks like both FTD devices can be polled successfully by Zabbix.
The FMC SNMP settings need to be configured under System > Configuration > SNMP.
Configure the SNMP parameters, save then test.
let me know how you get on.
I can only set the SNMP version and the community string. Nothing else. I cannot specify the Zabbix server as an SNMP server for our FirePower.
After I set this up, still no joy.
Still in the configuration area of the FMC, within Access List, put the Zabbix IP address in for SNMP. Save, then re-try.
You should be able to use the Cisco ASA template for Zabbix to monitor Cisco Firepower Threat Defense (FTD) devices.