Converts phytoene into all-trans-neurosporene as the major product, via the intermediary of phytofluene and zeta-carotene, by the introduction of three double bonds. 15-cis-phytoene + 3 A = 3 AH2 + all-trans-neurosporene Carotenoid biosynthesis. Belongs to the carotenoid/retinoid oxidoreductase family.