  We propose an extension to the Davydov D$_2$ Ansatz in the dynamics study of
the Holstein molecular crystal model with diagonal and off-diagonal
exciton-phonon coupling using the Dirac-Frenkel time-dependent variational
principle. The new trial state by the name of the "multi-D$_2$ Ansatz" is a
linear combination of Davydov D$_2$ trial states, and its validity is carefully
examined by quantifying how faithfully it follows the Schr\"odinger equation.
Considerable improvements in accuracy have been demonstrated in comparison with
the usual Davydov trial states, i.e., the single D$_1$ and D$_2$ Ans\"atze.
With an increase in the number of the Davydov D$_2$ trial states in the
multi-D$_2$ Ansatz, deviation from the exact Schr\"odinger dynamics is
gradually diminished, leading to a numerically exact solution to the
Schr\"odinger equation.
