The easiest models to import into Studio are OBJs that you make in Leopoly.
When in Studio, click on the “Import Model, Photo, or Audio Clip” button in the backpack. This launches a file browser dialog. Navigate to the location you saved your model file and select it.
The model types that work the best in zSpace are STL, DAE, and OBJ (specifically from Leopoly 3D).
For detailed information on importing models, see https://cdn.zspace.com/downloads/documentation/edu-resources/zSpaceStudioModelFileImportingGuide2017_v3.pdf