Hi Alexander,
Please see, comparison in QGIS:
Please see opening output in mygeodata website failed.
Test data (input/output/QGIS)
5105 Kmz -TopoJson.zip (878.3 KB)
Thanks,...problem is here: The topoJson format with 3D geometry can’t be render...It’s actually correct topoJson file and can be usefull for conversion...