Okay....

If you create a mesh in Maya and then zbrush it, you should and ideally replace it with the zbrush one, do this via a blendshape or transfer attributes to shrink wrap the verts. Obviously output an OBJ for this.

If you have used the rebuild topology command the blend shape option will not work as the point order will get reordered in Zbrush and will make a mess of your model in Maya.

Creating a displacement map will not help the changes to the base mesh as the mesh will get pulled around significantly during the sculpt, uvs are also affected and will need adjusting in maya. Any changes to the base mesh must be taken into consideration first, then once you start creating maps the result will be far more accurate and what you would expect to see

hope that helps

Jay