How quickly did you go up your subdivision levels in ZBrush? Comparing the two shots, the areas that have most recognisable detail are the areas where there is densest geometry (around the eyes/mouth). It looks almost as if there is high level detail there, but no lower level info to sustain it... did you spend much time working at the lower/middle subdivision levels?


Edit: Have you tried exporting out your mesh at maybe level 2,3, or 4 from Z...to see if you get better results off of those?