Comparison of the PLZ and PWZ relations derived in this work with empirical PLZ and PWZ relations provided by Ngeow et al. (2022) from RR Lyr in 46 globular clusters. Black lines mark the PLZ and PWZ relations derived in this work for a constant metallicity of [Fe/H] = −0.5; −2.0 dex; gray, shaded areas: metallicity slope c_λ ± δc_λ from Equation (8); red lines: empirical PLZ relation from Ngeow et al. (2022) for a constant metallicity of [Fe/H] = −0.5; −2.0 dex; red, shaded areas: metallicity slope c ± δc from Table 4 in Ngeow et al. (2022).