Comparison between observed [Eu/Fe] and [Zr/Fe] vs. [Fe/H] trends and the predictions of the Pareto optimal models (magenta lines). The thicker magenta lines show the predicted [Eu/Fe] and [Zr/Fe] vs. [Fe/H] trends for the Pareto optimal model with the smallest distance to the ideal point (0, 0) in objective space. The solid green curve shows the best-fit model to Eu and its corresponding prediction for Zr, while the dashed blue line represents the best-fit model to Zr and its prediction for Eu. The lower light blue lines represent the results of the model in case there is only the s-process contribution. Grey circles with error bars show the average observational values in metallicity bins. Residuals relative to the binned observations are displayed in the lower panels. Symbols for the observational data are the same as in Figure 3.