I wrote up a short and dirty script in order to archive out all the Zoneminder events as mpeg files. The script goes through and identifies all the events and creates a mpeg video file for each day of footage per camera (monitor). I found this was the best way to keep the event organized and able to look up a particular day and monitor the easiest. This is sort of a work in progress though, and for one of the awk statements, I had trouble incorporating the variable, so you may need to change it up slightly.
A prerequisite is that you will need to have FFMPEG installed on your system. You may also have to change some of the parameters to match your systems, such as where the root directory for the event image files are as well as adjusting for the number of EVENT_IMAGE_DIGITS you are using in your zoneminder options/configuration. I use 5 digits, but I believe the default is set to 3, which limits your events to 999 images. Anyway, here it is.
Maybe you can find this useful.