Refractory transition-metal (TM) diborides have high melting points, excellent hardness, and good chemical stability. However, these properties are not sufficient for applications involving extreme environments that require high mechanical strength as well as oxidation and corrosion resistance. Here, we study the effect of Cr addition on the properties of ZrB₂-rich Zr_1-xCr_xB_y thin films grown by hybrid high-power impulse and dc magnetron co-sputtering (Cr-HiPIMS/ZrB₂-DCMS) with a 100-V Cr-metal-ion synchronized bias. Cr metal fraction, x = Cr/(Zr + Cr), is increased from 0.23 to 0.44 by decreasing the power P_ZrB2 applied to the DCMS ZrB₂ target from 4000 to 2000 W, while the average power, pulse width, and frequency applied to the HiPIMS Cr target are maintained constant. In addition, y decreases from 2.18 to 1.11 as a function of P_ZrB2, as a result of supplying Cr to the growing film and preferential B resputtering caused by the pulsed Cr-ion flux. ZrB_2.18, Zr_0·77Cr_0·23B_1.52, Zr_0·71Cr_0·29B_1.42, and Zr_0·68Cr_0·32B_1.38 films have hexagonal AlB₂ crystal structure with a columnar nanostructure, while Zr_0·64Cr_0·36B_1.30 and Zr_0·56Cr_0·44B_1.11 are amorphous. All films show hardness above 30 GPa. Zr_0.56Cr_0.44B_1.11 alloys exhibit much better toughness, wear, oxidation, and corrosion resistance than ZrB_2.18. This combination of properties makes Zr_0·56Cr_0·44B_1.11 ideal candidates for numerous strategic applications.