Catalyzes the hydroxylation reaction from beta-carotene to zeaxanthin via beta-cryptoxanthin. all-trans-beta-carotene + 4 H(+) + 2 O2 + 4 reduced [2Fe-2S]-[ferredoxin] = all-trans-zeaxanthin + 2 H2O + 4 oxidized [2Fe-2S]-[ferredoxin] Carotenoid biosynthesis; astaxanthin biosynthesis. Belongs to the sterol desaturase family.