The reason why it isn't exporting is because your materials aren't set up properly. There are a multiple warnings for incorrectly set up materials while exporting and one error (which ultimately prevents the export completely), the material "misc 2 generic" has no shader information. Here's some info about material and shader setups: http://forum.zmodeler3.com/viewtopic.php?f=31&t=7350
There is one big other thing: Your added equipment is not going to work, it needs to be attached and compounded. Take a look at this: http://forum.zmodeler3.com/viewtopic.php?f=31&t=7353
Manually saved z3d files usually have a lower size, since they are compressed (unlike auto saves). In this case, it seems like all textures are stored in the z3d file instead of being seperate. I have to admit, I have never seen that before and I have no clue how to change it.
[staffnotice]
Lastly, please don't post a car's complete z3d file without any credits. It's usually sufficient to post a picture of the messaging bar at the bottom in case of errors during import or export, for further issues screenshots of the hierachy and the material browser are helpful. I have removed the link.[/staffnotice]