An .fhz file? you do not have not have an .fhm file inside the downloaded folder for the map? That is mostly the main file you need in order to open the map in the game, besides the objects, if the creator of the map put objects, the objects are optional though. (in my theory) as well as the music files, water material, & sky/weather. Those are mostly the most recent known stuff that are suppose to be with a map. I have never actually heard of an .fhz file before...but I am sure you may need some different program in order to open the .fhz file...