In this work we study two-step hydrogenation of an unsaturated precursor molecule with para-enriched hydrogen gas using ZULF NMR. This is done by continuously bubbling the hydrogen gas into samples containing dissolved dimethyl acetylenedicarboxylate (DMAD) along with the appropriate catalyst, and observing the NMR signals of the hydrogenation products (dimethyl maleate and dimethyl succinate) over time with a commercial atomic magnetometer . Magnetic shielding and compensating coils are used to create the 'zero-field' region, with residual magnetic-field intensity on the order of 10-100 pT, although the magnetometer can operate in fields up to 50 nT. A schematic of the experimental setup is shown in Fig. .