You're not going to make much progress from a decompiled map. I was working on maps for CA/ZK back in 2007/2008. Check out the forums for a variety of tutorials on mapping...
When you compile a map you take a number of bitmaps, split them into tiles, compress said tiles, and package them in the listed files. Decompliation from tiles to bitmaps is probably possible but I don't remember a working utility for it.
