The pressurized behaviours of structure, vibration and electrical transport in zirconium disulfide have been systematically investigated in a diamond anvil cell (DAC) under different hydrostatic environments up to 25.3 GPa utilizing in-situ Raman spectroscopy, electrical conductivity measurement, high-resolution transmission electron microscopy (HRTEM) and first-principles theoretical calculations. Upon compression, our experimental results showed that ZrS₂ underwent a phase transition accompanied by a semiconductor-to-metal transformation at 15.4 GPa under non-hydrostatic condition. Under hydrostatic condition, the corresponding phase transition occurred at a higher pressure of 17.5 GPa, indicating that the high-pressure phase transition is sensitive to the hydrostaticity in the sample chamber of DAC. Upon decompression, some absolutely new Raman peaks emerged at the pressures below 4.8 GPa and 2.9 GPa under non-hydrostatic and hydrostatic environments, respectively, which revealed an irreversible phase transition in ZrS₂. Furthermore, our observations from selected-area electron diffraction patterns confirmed the irreversibility of the high-pressure phase transformation.