Hasta La Motion!

Hi,
for the sake of rendering times, we have just rendered a slow motion sequence out of vray at normal speed and i am retiming it usig kronos.

Of course, retiming the rgb channels went smooth and sequence looks ok.
But now i am trying to apply zblur to the slow segment and i am having trouble slowing down the zdepth

I have tried to aply the zblur before retiming, but times of calculation goes up, i suppose triggered by the semitransparent alpha. Also, more arfifacts are aparent with the pre-blured version.

I have tried to retime the z channel using a cloned node from the rgb analysis, but results are extrange and unusable.
At the moment i am testing with the _vectorGenerator and trying to use the exact vector data on all channels, but can´t get to a nice result yet.

I have the VrayVelocity pass if i can feed it to the motion estimator to help with the calculations, but so far i wasn´t able to translate that info to furnace´s vectors format.

I am asking if anyone can help with some info or thoughts about this workflow. By this time rendering the whole slow motion sequence is not a possibility i´m affraid.

Thanks in advance
T