Complex sentence: The early 4th century in Egypt began with renewed persecution under the Emperor Diocletian and, in the Ethiopian/Eritrean Kingdom of Aksum, King Ezana declared Christianity the official religion after having been converted by Frumentius, resulting in the foundation of the Ethiopian Orthodox Tewahedo Church.
Split into simpler sentences: The early 4th century in Egypt began with renewed persecution under the Emperor Diocletian. In the Ethiopian/Eritrean Kingdom of Aksum, King Ezana declared Christianity the official religion after having been converted by Frumentius, resulting in the foundation of the Ethiopian Orthodox Tewahedo Church.