Cyclohexa-1,3-diene is treated with $\mathrm{O}{}_3$ followed by $\mathrm{Zn}/\mathrm{H}{}_2\mathrm{O}$. The organic products are

Both double bonds are cleaved and each carbon becomes C=O. The two carbons C-2 and C-3 between the double bonds end up as $\mathrm{OHC}-\mathrm{CHO}$ (ethanedial). The other four carbons C-4, C-5, C-6 and C-1 form $\mathrm{OHC}-\mathrm{CH}{}_2\mathrm{CH}{}_2-\mathrm{CHO}$ (butanedial).