Complex sentence: With the famous sonnet 18 ("Shall I compare thee to a summer's day") the tone changes dramatically towards romantic intimacy, and sonnet 20 laments that the young man is not a woman.
Split into simpler sentences: With the famous sonnet 18 ("Shall I compare thee to a summer's day") the tone changes dramatically towards romantic intimacy. Sonnet 20 explicitly laments that the young man is not a woman.