Zinc-to-iron (bottom) and zinc-to-silicon (top) ratio for our sample of proximate H₂ systems (circles with error bars). The colour scale provides the value of A_V/N(H), which is a proxy of the dust-to-gas ratio. For two systems, the derived A_V values are negative (hence unphysical) and the corresponding points are empty. Green triangles represent measurements in intervening DLAs (De Cia et al. 2016), and filled triangles correspond to known H₂ intervening systems (Balashev et al. 2019). The solid blue lines show the best linear fit to the value for the proximate H₂ systems, taking uncertainties on both axes into account. The green lines and shadowed region show the best linear fit and associated 1σ uncertainty for the overall sample of intervening DLAs.