I have owned both lenses for several months now (the CV 125 for almost 2 years, the Zeiss Apo 135 for maybe 4 months).
If I were to select one lens to own, over the other, it would be the CV 125, hands-down, no contest (it does almost everything the Zeiss does, as good as or better than, and then some).
In the Zeiss' favor, it is sharper and contrastier (JJChan and Michael Erlewine give some general feedback in this regard), but the bokeh is not as smooth ... and sometimes the color/contrast are too much.
The bottom line is this: if you do not shoot close-focus, the Zeiss is the better lens.
However, if you shoot close-focus, or are into macro in any way, the Voigtländer Apo Macro is the way to go. It isn't even a contest.
Since my photography is mostly macro, at 1;1 or greater, the Zeiss sits around and doesn't get used much.
If I am shooting macro over 1;1, say 1:2 or 1:4, sometimes both lenses tell me they want to be used.
Here are the differences in 70mm [1:2 lifesize subjects. The first two images were taken with the Zeiss 135 Apo + 12mm ext; the second two images were taken with the CV 125 (all shots @f/4).]
All involve the same subject, taken the same day, all are stacks, all with different perspectives.