ذَلِكَ بِأَنَّ اللَّهَ هُوَ الْحَقُّ
...
That is because Allah -- He is the Truth,
meaning, the true God, besides Whom no one deserves worship. He is the Possessor of the greatest sovereignty; whatever He wills happens and whatever He does not will does not happen. Everything is in need of Him and submits to Him.
...
وَأَنَّ مَا يَدْعُونَ مِن دُونِهِ هُوَ الْبَاطِلُ
...
and what they invoke besides Him, it is false.
meaning, the idols and false gods. Everything that is worshipped instead of Him -- may He be exalted -- is false, because it can neither bring benefit nor cause harm.
...
وَأَنَّ اللَّهَ هُوَ الْعَلِيُّ الْكَبِيرُ
And verily, Allah -- He is the Most High, the Most Great.
This is like the Ayat:
وَهُوَ الْعَلِىُّ الْعَظِيمُ
and He is the Most High, the Most Great. (42:4)
الْكَبِيرُ الْمُتَعَالِ
the Most Great, the Most High. (13:9)
Everything is subject to His might and power; there is no God except Him and no Lord besides Him, because He is the Almighty and there is none mightier than He, the Most High and there is none higher than He, the Most Great and there is none greater than He. Exalted, sanctified, and glorified be He far above all that the evildoers say.