I tested this in my TinyDNS setup and worked great.

# verbose tinydns data file

#
# REVERSE ZONE
#
# (reverse) dns servers: primary and secondary
Z45.168.192.in-addr.arpa:ns.example.net:hostmaster.example.net::::::::

# NS records
&45.168.192.in-addr.arpa::ns.example.net:::
&45.168.192.in-addr.arpa::ns2.example.net:::

# MX handlers
@45.168.192.in-addr.arpa::relay.example.net:10
@45.168.192.in-addr.arpa::relay2.example.net:20

#
# FORWARD ZONE:
#
# SOA record: primary nameserver is ns.example.net and hostmaster
# mail address is hostmaster@example.net
# (the ‘Z’ configuration line is the only one that
# allows specifying the hostmaster mail address)
Zexample.net:ns.example.net:hostmaster.example.net::::::::

# NS records: primary and secondary nameservers
&example.net::ns.example.net:::
&example.net::ns2.example.net:::

# MX records: relay.example.net, distance = 10
# relay2.example.net, distance = 20
@example.net::relay.example.net:10
@example.net::relay2.example.net:20

# A records: ns.example.net, ns2.example.net
=ns.example.net:192.168.45.1:::
=ns2.example.net:192.168.45.2:::

# PTR records: relays are in the same hosts as dns servers
+relay.example.net:192.168.45.1:::
+relay2.example.net:192.168.45.2:::

# more A records: gateway.example.net
=gateway.example.net:192.168.45.254:::

# CNAME record: nscache.example.net is alias to gateway.example.net
Cnscache.example.net:gateway.example.net:::

#
# SUB DOMAIN DELEGATION
#

# NS record
&dmz.example.net::ns.dmz.example.net:::

# A/PTR record for nameserver
=ns.dmz.example.net:192.168.90.1:::