Surah Az Zukhruf Tafseer

وَهُوَ الَّذِي فِي السَّمَاء إِلَهٌ وَفِي الاَْرْضِ إِلَهٌ

It is He Who is the only God in the heaven and the only God on the earth.

means, He is the God of those who are in the heavens and the God of those who are on earth; all of them worship Him and are humbled before Him.

وَهُوَ الْحَكِيمُ الْعَلِيمُ

And He is the All-Wise, the All-Knower.

This Ayah is like the Ayah:

وَهُوَ اللَّهُ فِى السَّمَـوَتِ وَفِى الاٌّرْضِ يَعْلَمُ سِرَّكُمْ وَجَهْرَكُمْ وَيَعْلَمُ مَا تَكْسِبُونَ

And He is Allah in the heavens and on the earth; He knows what you conceal and what you reveal, and He knows what you earn. (6:3)

which means, He is the One who is called Allah in the heavens and on the earth.