FWIW -
In Civil 3D 2015 I use the new
EXPORTKML Command - See Toolspace, Toolbox, Miscellaneous Utilities, Export KML, right click the nested Export KML, select Execute... menu item - to export projects to .KMZ, etc. for our clients.
I also use QGIS & ArcGIS trial installed on VM
; the latter to extract data from .GDB which I've not (yet) found a way to do from QGIS.
Cheers