all-trans-zeta-carotene + 2 AH2 => 15-cis-phytoene + 2 A
all-trans-zeta-carotene + 2 ah2 => 15-cis-phytoene + 2 a
all-trans-zeta-carotene + 2 AH2 => 15-cis-phytoene + 2 A
all-trans-zeta-carotene + 2 ah2 => 15-cis-phytoene + 2 a