The original .LS file had password encryption. Fix: You must enter the original project password during the ZMCO recovery process. Without it, Lumion will not unpack the geometry.
Architects often complain that ZMCO files eat up hard drive space. A single ZMCO can be 500MB to 2GB. After you finish a project and export your final renders: lumion zmco
Here is everything you need to know about the Lumion ZMCO file. The original