I think is better to use Zentyal as PDC, local DNS, DHCP (File server, ...) for LAN, with DNS forwarder to pFsense and pFsense as UTM.
I use some kind of configuration (Endian as UTM with 4 zones: RED, GREEN, ORANGE, BLUE; Zentyal as multidomain email server in ORANGE (DMZ); NethServer 7rc2 as PDC/AD/File Server in GREEN).