You should be creating your normals in zbush and using goz (I think thats what its called). The work flow should be some thing like this

1:Create mesh in maya (check normal)
2:Create UVs in maya (better then using zbrush UV master)
3:Export to zbrush
4:Subdivide as meny times as you need in z and model (do not delete subdivion history)
5.Drop down to subd 1 then create normal or misplacement map
6:Goz back to maya
...................dave