D₄₀₀₀ vs. [ O III ] λ 5007/Hβ  diagram used to break the R₂₃  degeneracy for the 0.5 <z< 0.9 zCOSMOS galaxies (cyan points) without NIR spectroscopy. The 39 zCOSMOS galaxies with ISAAC spectroscopy are shown as blue filled circles for galaxies with low (branch) O/H measurements, red filled circles for galaxies with high (branch) O/H measurements, and green filled circles for the six galaxies with double-valued solutions (note that the D₄₀₀₀ and [ O III ] λ 5007/Hβ  values of two galaxies are almost identical, i.e., the respective green circles coincide). This diagram can be used to break the lower/upper branch R₂₃  degeneracy of other 0.5 <z< 0.9 galaxies without NIR spectroscopy, but similar D₄₀₀₀ and [OIII]/Hβ  as the 33 benchmark galaxies with ISAAC spectroscopy and reliable metallicities.