Example of inclination evolution of the six planets in the HIP 41378 system. In this example, the Lagrange-Laplace equation is solved using the nominal masses and semi-major axes of all planets given in Table 1. The initial conditions ζ_k are set from the nominal inclinations I_k (all assumed to be I_k ⩽ 90°) and random longitudes of node Ω_k in a 0.2°-wide interval; this choice is commented in Sect. 5.