His approaching departure did not prevent his amusing himself, but rather gave zest to his pleasures.
Firmly convinced as he was of the truths revealed to him by his benefactor, and happy as he had been in perfecting his inner man, to which he had devoted himself with such ardor—all the zest of such a life vanished after the engagement of Andrew and Natasha and the death of Joseph Alexeevich, the news of which reached him almost at the same time.
There are no more uses of "zest" in the book.
Show samples from other sources
If you didn’t know her, you’d think her zest comes from malice.
Susan Ee -- Angelfall
Kit chose the stories she herself enjoyed most, and her reading had a zest and liveliness that enthralled the children.
Elizabeth George Speare -- The Witch of Blackbird Pond