We report a post-treatment method for modifying the crystalline nature and texture of ZnO nanostructure surfaces. Single crystalline ZnO structures were transformed using a solution-based reaction in an aqueous sodium selenite and hydrazine solution into single crystalline ZnO/polycrystalline ZnSe (core/shell) heterostructures (as an intermediate material), which were then used to texture the surfaces of ZnO nanostructures. The ZnO/ZnSe nanostructures were calcined to obtain pure ZnO nanostructures with a variety of surface crystalline natures and textures under controlled calcination conditions. Single crystalline ZnO core/polycrystalline ZnO shell nanostructures, single crystalline ZnO with wavy surfaces/ZnO nanoparticles, or single crystalline ZnO nanostructures with wavy surfaces were obtained by calcination at 550, 700, or 800 C, respectively. The experimental results suggest a possible mechanism by which the surface of the ZnO nanostructures was modified. This method potentially may be extended to any single crystalline ZnO nanostructures