Catalyzes the conversion of zeta-carotene to lycopene via the intermediary of neurosporene. It carries out two consecutive desaturations (introduction of double bonds) at positions C-7 and C-7'. Shows stereoselectivity toward trans C15-C15'zeta-carotene double bond. The zeta-carotene produced by the phytoene desaturase PDS has a C15-C15' double bond in the cis configuration and it requires isomerization before being recognized as substrate by ZDS. No activity with all-trans-zeta-carotene. The main product is 7,9,7',9'-tetra-cis-lycopene (pro-lycopene). 9,9'-di-cis-zeta-carotene + 2 a quinone = 7,7',9,9'-tetra-cis-lycopene + 2 a quinol Lipophilic quinones such as decyl-plastoquinone or decyl-ubiquinone. Carotenoid biosynthesis; lycopene biosynthesis. Monomer and dimer. Belongs to the zeta carotene desaturase family.