Superionic conduction in solid-state materials is governed not only by static factors, such as structure and composition, but also by dynamic interactions between the mobile ion and the crystal lattice. Specifically, the dynamics of lattice vibrations, or phonons, have attracted interest because of their hypothesized ability to facilitate fast ionic conduction. Herein, we use laser-driven ultrafast impedance spectroscopy (LUIS) to resonantly excite phonons using a THz field and probe ion hopping with picosecond time resolution. We apply LUIS to understand the dynamical role of phonons in Li₇La₃Zr₂O₁₂ (LLZO). When in its cubic phase (c-LLZO), this garnet-type solid electrolyte has an ionic conductivity two orders of magnitude greater than its tetragonal phase (t-LLZO). Upon excitation of phonons in the 0.5-7.5 THz range, the ionic conductivity of both polymorphs is enhanced. Furthermore, we observe a similar time decay constant of the perturbation between t-LLZO and c-LLZO despite their distinct Li sublattices and migration mechanisms. Along with Raman spectra and MD-computed vibrational density of states, these findings suggest that low-energy optical phonons perturb the lattice to enhance ionic conduction independently of the underlying static properties. We propose that it does so by increasing the population of phonons which directly modulate the ion hopping pathway and by increasing the entropy of migration thereby partially counteracting the migration barrier set by the Li sublattice. Overall, this work highlights the interplay of static and dynamic factors that enables improved ionic conductivity in both highly and poorly conducting inorganic solids alike.