Zest : great enthusiasm and energy. Restive : (of a person) unable to remain still, silent, or submissive, especially because of boredom or dissatisfaction. Callous : showing or having an insensitive and cruel disregard for others.
Indifference : lack of interest, concern, or sympathy. Distaste : mild dislike or aversion.
Antonym of Zest is Distaste