Without having to look at the meshfiles, this clearly is a normals problem, and it's getting quite obvious where it comes from
I assume that during the Maya -> Max -> ZMod conversion, you converted the Maya file to .fbx or .obj ( in case you didn't, you'd better use one of these filetypes, not that it will matter later on) , in 3DS Max you had to make to conversion to .3ds and imported that file into ZModeler. As I said in another thread, if you're making a car in Maya or 3D Studio Max, your conversion to .3ds will lose all informations about the smoothing. So in case you're sure Zmodeler will be used for the development of a car, do all smoothing there.
Added to this, even if you do export your car from 3DS Max to game format ( like with rFactor ), most racing games can only read one smoothing group. So setting any smoothing option in 3DS Max or Maya to 'AUTOMATIC', will not work aswell.
In Zmodeler you should check the smoothing before you export to .gp4 format, you can do so by clicking the Surface -> Normals -> Calculate. This is the result I get :
Best regards,
Koen
Game Stock Car: Formula Reiza - Formula ExtremeMMG F1 2008: 3D: Toyota, Force India, Ferrari, Williams, RBR, STR - 2D: Toyota, Williams, Super AguriFSOne 2007: 3D: Ferrari, BMW - 2D: Ferrari, BMWRH 2006: 3D: All cars (cancelled) & RH 2005: 3D: All cars except Ferrari