Let me start off by saying how much of a fan I am of Zayn Malik and Zhavia Ward.
Zayn is my favourite One Directioner and is the only one from the group whose music I actually like - based on the fact I have more than one of his songs in my music library.
Often referred to by former bandmate Louis Tomlinson as the voice of the band, Zayn's lower register is the weakest of his range but his falsetto is stand out - just YouTube search Zayn Malik and high notes and you'll come across plenty of examples with his One Direction bandmates watching in awe.
As for Zhavia, I watched reality television singing competition The Four religiously and fell in love with her musical style and voice. Zhavia, whose lower register is hard to beat, was confident and I was always excited to see how she would make whatever song she was covering that week her own. She was only 16 on the show. She didn't win but she was by far the stand out on the show ... which is why she was given a record deal pretty quickly.