Do you mean a bitmap texture or Polypaint? You can project Polypaint from the high onto the new low mesh but the UVs are destroyed when using zRemesher.
As long as you UV the model after retopologizing it, you can bake the texture from the highpoly model to the low poly model regardless of how different the UVs are (in fact, the highpoly model doesn't even need UVs if you're using polypaint). The important thing is that the meshes' geometry occupy the same space. Then any…