As a last try I managed to make it a little bit better (especially the nose is more alike the ZBrush-HiRes nose, see 2 posts above) by putting in the AdvancedMaterialRoom a Subtract-node with Value1=1 and Value2=0,5 in between the Displacement and the Map,  as Stonemason suggested earlier. Actually I don't know why it works better ...

BTW: The displacement strength is set to 1,2