The bridge tool may have set your face vertices to point directly forward, making the faces look like they are artificicicieded...
Import and export to and from Z kinda prooves it as the program will re evaluate the normals on import and hence when exported its fine.
Try BennyK's suggestion it should sort out the issues.
Chris (formerly R@nSiD)
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Winner SM VFX Challenge 1
3rd Place SM SteamPunk Challenge (May 2007)