"Then what is the matter with you? How do you judge?" meaning: you acknowledge that Allah, Glorified and Exalted is He, is the Creator and the Provider, yet you worship idols besides Him!
﴿فَمَا لكم كَيفَ تحكمون﴾ أَيْ: أَنَّكُمْ تُقِرُّونَ بِأَنَّ اللَّهَ ﷿ هُوَ الْخَالِقُ وَالرَّازِقُ (ل ١٣٩) ثُمَّ تَعْبُدُونَ الأَوْثَانَ مِنْ دُونِهِ!