Complex sentence: Through her large eyes, Keane aimed to express Rapunzel's "irrepressible quality," a trait that was also present in Mandy Moore's voice, which allowed Keane to use her as inspiration.
Split into simpler sentences: Through her large eyes, Keane aimed to convey Rapunzel's "irrepressible quality". He discovered a similar trait in Mandy Moore's voice, allowing Keane to use her as inspiration.