The snmp.conf can be very simple, For example mine is just:
com2sec local 127.0.0.1/32 public
group MyROGroup v1 local
group MyROGroup v2c local
group MyROGroup usm local
view all included .1 80
access MyROGroup "" any noauth exact all none none
syslocation MyLocation
syscontact Me
So its only accessible from localhost.
I have MRTG and SNMP working fine on my ZS box:
http://fios1.houkouonchi.jp/mrtg/
http://fios2.houkouonchi.jp/mrtg/