Complex sentence: Ursula's alter ego Vanessa is not included, thereby omitting the subplot of Eric's brainwashing by her, leading to a new ending where a singing contest of foreign princesses is held to see if Eric can recognize any of them to have Ariel's voice.
Split into simpler sentences: Ursula's alter ego Vanessa is not included, thereby omitting the subplot of Eric's brainwashing by her, as well as the subsequent end. Instead, there is a contest with foreign princesses singing songs to see if Eric can recognize any of them to have Ariel's voice.