The Zenoss package for Debian does not support the new insserv dependency specification. When installed alongside muni-node, as on our systems, this resulted in the following:
insserv: warning: script 'zenoss-stack' missing LSB tags and overrides
insserv: There is a loop between service munin-node and zenoss-stack if stopped
insserv: loop involving service zenoss-stack at depth 2
insserv: loop involving service munin-node at depth 1
insserv: Stopping zenoss-stack depends on munin-node and therefore on system facility `$all' which can not be true!
insserv: exiting now without changing boot order!
To fix this, I installed an overrides file in /etc/insserv/overrides/zenoss-stack as per http://wiki.debian.org/LSBInitScripts/DependencyBasedBoot:
### BEGIN INIT INFO
# Provides: zenoss-stack
# Required-Start: $local_fs $remote_fs
# Required-Stop: $local_fs $remote_fs
# Should-Start: $all
# Should-Stop: $all
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start/stop Zenoss-stack
# Description: Start/stop Zenoss-stack
### END INIT INFO
I'm not 100% sure that this is correct requirements for Zenoss, but it has resolved our dependency issues.