وَهُمۡ عَلَىٰ مَا يَفۡعَلُونَ بِٱلۡمُؤۡمِنِينَ شُهُودٞ
and they (themselves) are witnesses of what they have done to the believers.
وَمَا نَقَمُواْ مِنۡهُمۡ إِلَّآ أَن يُؤۡمِنُواْ بِٱللَّهِ ٱلۡعَزِيزِ ٱلۡحَمِيدِ
They took vengeance on them only because they believed in God, the Mighty, the Praiseworthy,
Holder of the throne, the Glorious,
Vowel Difference (harakat) - Grammatical Case Change
ٱلۡمَجِيدُ
the Glorious
ٱلۡمَجِيدِ
glorious
Changing the grammatical case of 'al-Majeed' from nominative (damma) to genitive (kasra) shifts the adjective 'glorious' so that it modifies the 'Throne' (which is in the genitive case) rather than the 'Holder' of the throne.
Abu Al-Harith, Duri Al-Kisa'i, Idris, Ishaq, Khalaf, Khallad
Vowel Difference (harakat) - Grammatical Case Change
مَّحۡفُوظِۭ
guarded
مَّحْفُوظٞ
preserved
In Hafs, the word is in the genitive case (kasratayn), acting as an adjective modifying the tablet ('a guarded tablet'). In the variant, it is in the nominative case (dammatayn), acting as a description referring back to the Quran itself ('[It is] preserved in a tablet').
Qalun, Warsh