Daniel,
I dug through my copy of 89D and couldn't find anything. I checked the manual and you can set up the codeplug to display up to 12 characters of the zone name, but it will shorten the channel name by whatever number of characters you specify for the zone.
I have the zones on my my radios organized by either county or service (e.g, ham radio.) What I do is to put a frequency that is either a county frequency or a ham frequency or something that I can recognize and know what zone it is in as the first channel of each zone. Another trick is to program in a dummy frequency, such as 136.000, receive only, with a inverted DPL tone (so the receiver never opens) and delete it from the scan list. Then give it the name of the service ("HAM RADIO" or "XYZ CO FD") or County ("XYZ COUNTY"). When you move the zone selector, that channel will show up first and identify the zone.