The detective was zealous in her pursuit of the kidnappers.
I was zealous in my demands on my sisters for promptness in rehearsals. I was passionate, intolerant of small talk, hungry for knowledge, grabby, bossy, precocious. —Lynn Margulis, Curious Minds, (2004) 2005
Sir Thomas was zealous in the pursuit of recusants, not poachers, and was otherwise an amiable man. —S. Schoenbaum, Shakespeare's Lives, 1991
Zealous in his ministerial labours, blameless in his life and habits, he yet did not appear to enjoy that mental serenity, that inward content, which should be the reward of every sincere Christian and practical philanthropist. —Charlotte Brontë, Jane Eyre, 1847
He had no cause for self-reproach on the score of neglect, or want of thought, for he had been devoted to her service; and yet a hundred little occasions rose up before him, on which he fancied he might have been more zealous, and more earnest, and wished he had been. —Charles Dickens, Oliver Twist, 1838