The vibrational averaging module of the Dalton Project was extended to work also with the Amsterdam Density Functional (ADF) program, making it possible to calculate vibrational corrections to properties and at the same time include a treatment of relativistic effects for heavier atoms at the level of the Zeroth-Order Regular Approximation (ZORA). To illustrate the importance of the relativistic contributions, zero-point vibrational corrections were calculated for the electric field gradient tensor and the two NMR parameters, the isotropic shielding and the spin-spin coupling constants (SSCC), of selected mercury compounds. For all three properties, the vibrational corrected values performed closest to experimental values, and the magnitudes of the corrections depended on the level of relativity and the basis set in the calculation.