Complex sentence: The Myōshin-ji school is the largest school in Rinzai Zen, contains within it more than three thousand temples throughout Japan, along with nineteen monasteries.
Split into simpler sentences: The Myōshin-ji school of Rinzai Zen Buddhism is the largest school in Rinzai Zen. This particular school contains within it more than three thousand temples throughout Japan, along with nineteen monasteries.