does somebody have experience with creating IFCZIP files (xyz.ifczip) ? I can only export usual IFC 2x3 or IFC 4 out of my SU 2023. Is there maybe an add-on or something that can help me? I already checked online for converters but no success…

Solibri has a free application called “Solibri IFC Optimizer” that can save your IFC as an IFCZIP file. I don’t know if it is any different from what happens if you just use ZIP compression on your IFC file and then rename the file extension.

Why does it have to be an .IFCzip file and not an .IFC

For a better IFC export from SketchUp, it is recommended to use the IFC Manager Extension.
You can easily download this via Releases · BIM-Tools/SketchUp-IFC-Manager · GitHub