Vibronic wavepacket dynamics after photo-excitation is simulated in the diabatic basis using ElVibRot . The diabatic densities are transformed to the adiabatic representation for the comparison with the trajectorybased approaches. The nuclear wavepacket has been expanded in a two-dimensional basis set formed by the direct product of two uni-dimensional basis sets for each diabatic state. The harmonic-oscillator basis set has been used for q (40 basis functions), and a Fourier-series, periodic basis set has been used for ϕ (512 basis functions); the number of grid points along each coordinate is 80 and 552, respectively for q and ϕ. The propagation was performed with the Chebychev scheme for which the evolution operator is expanded on Chebychev polynomials with time step 0.1 fs. The Hamiltonian needs to be renormalized so that its spectral range lies in the interval [-1, 1]. Figure reports snapshots of the nuclear dynamics at times t = 10, 50, 100 fs, where the contour lines represent the adiabatic components of the nuclear density (in S 1 in the upper panels and in S 0 in the lower panels) and the colormaps represent the adiabatic PESs (S 1 in the upper panels and S 0 in the lower panels). The initially excited density on S 1 (t = 10 fs) extends over time towards the CIs (t = 50 fs) and finally funnels via the CIs to S 0 (t = 100 fs). While the dynamics shows coherent oscillations along q, the isomerization reaction from the cis to the trans conformer is characterized by the wavepacket reaching the values |ϕ| > π 2 . The isomerization process just described will be analyzed in detail employing the exact factorization, in Section III A by looking at TDPES and TDVP, and in Section III B by using quantum and coupled trajectories.