The light soon died away, but the look of suffering remained, and Zossimov, watching and studying his patient with all the zest of a young doctor beginning to practise, noticed in him no joy at the arrival of his mother and sister, but a sort of bitter, hidden determination to bear another hour or two of inevitable torture.
"I should say, too," continued Zossimov with zest, "that your complete recovery depends solely on yourself.
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