ZMP Files - presumably for Zone Map - link map data to location info from AreaTable.dbc. There are 3 of those files in 1.12.2:
Interface\WorldMap\Expansion01.zmp (in patch.MPQ, no data present)
The files are headerless. They contain 128 x 128 uint32 values (double resolution compared to WDT) which are area IDs from AreaTable.dbc
We think it is possible that this file is used by the client to display the name of the current area while moving in the World.
WowDev Wiki says:
They are used on parsing WorldMapArea.dbc. The values get copied and then get overwritten with the WorldMapArea-id the areaid they referenced is in. It will hold a zero or the WMA-id depending on if the area and the map that's currently parsed match. This also takes the virtual map id into account.
Edited by antz