An ultrafast anisotropic electro-optic effect of the zinc sulfide crystal is predicted employing a numerical pump-probe simulation. The numerical results indicate that the time-dependence of the anisotropic response of ZnS exhibits a phase shift with respect to the pump laser field. The phase shift coincides with the time-resolved dynamical Franz-Keldysh effect, which is the modulation of the isotropic part of the dielectric function. While the probe frequency dependence around the band gap is not intense, it becomes intense at higher photon energies of approximately 42~eV.