Once you have your low-poly model back in Blender (with the high-res details projected), use Blender's native UV tools. Then, use the Z3D plugin's function.
Regular updates have fixed previous serialization and deserialization errors. Cons: blender z3d plugin hot
The ghost was a plugin called .
: Go to Edit > Preferences > Add-ons , click Install , and select your downloaded file. Once you have your low-poly model back in