Adiabatic potential of K2ZnF4:Cu2+ impurity system is calculated within the frames of pair potential approximation and shell model. The Jahn-Teller multi-body energy contribution is approximated by the lower branch of [CuF6] cluster adiabatic potential. It is shown that Qθ- and Qε-displacements of the distorted octahedron of F ions surrounding Cu impurity ion may be assumed as the normal vibrational modes. Thus K2ZnF4:Cu2+ vibronic states energy spectrum calculation reduces to the solution of the (Exe)-problem with the adiabatic potential, which contains not only the main terms ( 1/2 ·K0·ρ2-|V e|·ρ) but also relatively small corrections (- 1/2 ·ΔK·ρ2cos(2φ) +F·ρ -·cosφ) treated by perturbation theory. g-tensor components temperature dependences calculated by averaging over vibronic levels are consistent with the experimental data. Simulation of hydrostatic pressure influence on the K2ZnF4:Cu2+ properties predicts essential changes in g-tensor components values and temperature dependences.