ZBrushCentral

Normalmap to defferrent toporogy

begin to use Zbrush at work and am a beginner for a little more than one year.
Although modeling is sometimes plentifully carried out from zero, the re-modeling of the character data of a game is sometimes carried out.
Although the modeling of the data is got and carried out from the software maker, it is a very rude triangular polygon of 300k to 400K most.
There are also a normal map, a vamp map, and a texture map in the data, and a few may become good touch if a rendering is carried out.
In order for me to think, it regards that there is such a map as the model of a high polygon being once made by the software side, but as for software makers, the high poly data is not passed stubbornly.
Unavoidably, SDiv the rude data to Level6 and it changes it into Polypaint from UV texture, An alpha mask is used from ProjectAll and its Plypaint, and the model which Retopoed the model with same location by ZRemesher is reengraved with a pattern once again.
I think that the very useless thing is done.
Isn’t there any method on which a normal map is reflected in a situation without a highly minute polygon?
If ZRemesher is used, he would like to lose UV information and to express the feeling of volume as a lump on a normal map, but if it ProjectAll, it will return to very rude form.
Although how to make a normal map from a high definition is written to the book, since it is but good for the model from which topology is different, isn’t there any method on which form is reflected?
I want help.