The 12-50 does not fit into the 14-42 Nauticam flat port (it is too long by very little). It does fit nicely in the 9-18 dome port (I did not test image quality of this combination).
As Phil wrote, the standard zoom gear will not work. However, I think it will be possible to build something (based on the zoom gear I have for the 14-42/9-18). Will report if I manage to get this working...
I am very interested in that. Please follow up on that as I am a little reluctant to pay $1000 for the dedicated port and gear.