Complex sentence: Long and nasalized vowels are generally diphthongized when stressed, except the vowel, the phoneme is also diphthongized in unstressed syllables, it is diphthongized to.
Split into simpler sentences: Long and nasalized vowels are generally diphthongized when stressed, except the vowel. The phoneme is also diphthongized in unstressed syllables, it is diphthongized to.