Influential early childhood books included The Color Kittens and The Tawny Scrawny Lion.
[5] At New Trier High School, Zelinsky was interested in natural history and architecture and saw himself following one of those paths for a career.
He took a class taught by Maurice Sendak on the history and art of children's books, and it inspired him to a career in the area.
His career in children's books began in 1978 with the illustrations for Avi's Emily Upham's Revenge.
[2] Zelinsky does not have a recognizable style, suiting his artwork and techniques to the particular nature of the book to be illustrated.
According to Linnea Lannon in the artist profile Detroit Free Press, "What has raised Zelinsky into the first rank of children's book illustrators is not just the pictures but the way they integrate with text.