Oscillations of eccentricity and mutual inclination for numerically propagated trajectories corresponding to ℋ = 1.8 with mass ratio at α_m = 1.1 for different initial eccentricities at e_1,0 = 0.436 (left panel) and e_1,0 = 0.2 (right panel). Both the initial conditions of g₁ and g₂ are assumed at π/2. Red points represent the trajectories numerically propagated under the octupole-order Hamiltonian, while the blue lines stand for the trajectories numerically propagated under the quadrupole-order model. For comparison, the characteristic curves of periodic orbit families associated with ZLK resonance and the conventional ZLK resonance centers are provided (see the solid black lines and the dashed lines, which are the same as the ones shown in Fig. 3).