How can you reduce the file size of a CAD model?

I would say the problem of bigger CAD files are exists only for data structure with mesh(or cloud of points) inside. The rest of formats are quite compact and is not big deal for modern hardware like SSD drive or SSD based RAIDs. As for the meshes for the softwares Geomagic like I would say good approach can be to align the 3Dscans with origin scanned data, then merging and decimation to accuracy similar to 3D scanner accuracy or required/enough accuracy. It is not a big sense to have supercloud of point when the points have been gotten by weak scanner similar to having high megapixels image from the camera with weak optics capabilities.

I found a small hack once - I introduced VR/ AR to a company and that required smaller files that were a serious problem as they were Large Assembly files. I found that turning the parametric assembly to a solid polygon model and then converted again to a prt file - it was then suppressed enough to be used in AR/ VR. Think outside the box

It makes no sense to ZIP SolidWorks files, for example, because they are already prezipped. You can check prezipping at your favorite CAD file systems' formats and comment it here. P.S. It makes sense to ZIP the STL files, they become 30% more compact.

I noticed, that SolidWorks file size which includes mesh (imported data in STL file format as example) can be significantly decreased if you hide the mesh, then save the file. Please note, it's enough just to hide the mesh, not suppress it. Therefore, I conclude that the mesh display/view properties such as colors and possibly something else require significant size during the saving at origin SW format along the mesh data itself such as point coordinates and so on. And vice versa, when you show the data then save, you can see the file becomes bigger. This feature can be used at file sending if the receiver is well informed what the data should be shown back. It was noticed at SW2020.