<p>Long-term effects induced by the coupling of gravitational harmonics can be significant in nonresonant orbits about bodies whose shape clearly departs from an Earth-like mass distribution. Based on a perturbation arrangement that assumes a mild dominance of the zonal harmonic of the second degree, the transformation that removes the short-period terms is derived for a degree and order 3 truncation of the expansion of the gravitational potential. Particularization of the ensuing mean dynamics for the gravity coefficients of the Moon illustrates the important differences that the coupling of nonzonal terms may introduce with respect to typical perturbed Kepler motions.</p>