Complex sentence: In addition to Islam, many Iraqi people are Christians belonging to various Christian denominations, some of which are the Chaldean Catholic Church (Chaldean Christians), the Syriac Orthodox Church, and the Assyrian Church of the East.
Split into simpler sentences: In addition to Islam, many Iraqi people are Christians belonging to various Christian denominations. Assyrians belong to the Chaldean Catholic Church, the Syriac Orthodox Church, and the Assyrian Church of the East.