Catalysis of the reactions: a 9-cis-epoxycarotenoid + O2 = 2-cis,4-trans-xanthoxin + a 12'-apo-carotenal; 9-cis-violaxanthin + O2 = 2-cis,4-trans-xanthoxin + (3S,5R,6S)-5,6-epoxy-3-hydroxy-5,6-dihydro-12'-apo-beta-caroten-12'-al; and 9'-cis-neoxanthin + O