The optimum sub-barrier fusion path is studied towards the synthesis of superheavy nuclei, within the multidimensional space of deformation, from two target-projectile nuclei up to the synthesized one. The influence of single-particle level scheme variation is introduced, as produced by two interacting Nilsson potential wells upon the total deformation energy. The pairing interaction is calculated within the deformed two-center shell model. The influence of discrete levels is added to the deformed charged liquid drop energy of Yukawa-plus-exponential type. Through the minimization of the potential energy surface in Wentzel-Kramers-Brillouin approximation, one has obtained the variation of two interacting nuclei up to the final superheavy element. Values of sub-barrier cross section are presented for some superheavy nuclei.