Allah says here:

﴿أَوَلَمْ يَكْفُرُواْ بِمَآ أُوتِىَ مُوسَى مِن قَبْلُ﴾

(Did they not disbelieve in that which was given to Musa of old) Did not mankind disbelieve in those mighty signs which were given to Musa

﴿قَالُواْ سِحْرَانِ تَظَـهَرَا﴾

(They say: "Two kinds of magic, each helping the other!'') cooperating or working one with the other.

﴿وَقَالُواْ إِنَّا بِكُلٍّ كَـفِرُونَ﴾

(And they say: "Verily, in both we are disbelievers.'') meaning, `we disbelieve in each of them.' Because of the close relationship between Musa and Harun, mention of one includes the other.