DDS isnt only emergency 4 file, its international image file like PNG or JPG. Emergency could have any image file as texture file, but the dds is more "unknow". (Battlefield 2 uses .dds too.) The texture file, has to be in the same folder where the model is, and if the texture shows only white, check that you have edited the .v3o file. (like if you have changed texture format etc) It should be default if you edited / applied the texture with zmodeler.