Complex sentence: According to legend, the diocese of Kashkar was founded by the apostle Mari in the first century and was the oldest diocese in Persia, preceding by several decades the establishment of a diocese in the Persian capital Seleucia-Ctesiphon.
Split into simpler sentences: According to legend, the diocese of Kashkar was the oldest diocese in Persia. It was said to have been founded by the apostle Mari in the first century, several decades before the establishment of a diocese in the Persian capital Seleucia-Ctesiphon.