Comparison between PGPUC and BaSTI results for non-standard chemical compositions. Left panel: evolutionary tracks with Y = 0.30 and Z = 9.2 × 10^-4. Middle panel: evolutionary tracks with Y = 0.35 and Z = 8.5 × 10^-4. Right panels: ZAHB loci for Y = 0.30 and Z = 9.2 × 10^-4 (upper panel) and Y = 0.35 and Z = 8.5 × 10^-4 (lower panel), where for comparison BaSTI ZAHB loci are moved Δlog (L/L_⊙) = −0.025. PGPUC ZAHB loci are shown for progenitor masses of M_i = 0.7 M_⊙ and M_i = 0.9 M_⊙.