Sorry I couldn't help more, just never used ZM3.
One thing that does spring to mind though. As you have nothing to lose, why not load up ZM3 & go through the process of building the car. I mean, load it up & then go through the process you used to build it, not actually doing it, but just check you didn't make any silly mistakes & everything looks right.
Also, if everything is backed up, maybe try changing &/or re-doing a few things or just simply re-exporting it. Maybe something is just a bit funky or the export just got messed up etc.