haven't been in the ZM server but I've been trying to get on the forums for the past hour only to succeed right now.
ZERO I've come to the conclusion that a clan is seriously trying to disrupt your server, through out the day there is constant lag even when my ping is 45 (I know a low ping doesn't mean a good and smooth connection) but I've never had lag before and there are alot of new players that come on now, don't know if it could be that its summer and people are online more, but I have the suspicion that there is a clan trying some shady shit.
You might wanna have a lookies into the subject when you get back or when you can.