Zack is a blue LNER tank engine. He is small, but very powerful. Zack is kind and gentle like Boco, even the trucks do not play tricks on him. Zack is also a member of Norramby branch line, and likes working with Molly the Holden D16. He appears to have a crush on her. Zack is a friendly and easy-going tank engine. He has a close friendship with Thomas, Percy, Edward, and Stanley, and even puts James in his place. Unusually, he wears glasses, because he has poor eyesight without them. Zack is a Holden rebuild of the LNER Holmes J83 tank engine. He is NWR no. 15. He is painted NWR blue with red lining, the letters "NWR" on his tank sides and the number "15" on his bunker sides. His friends are Thomas, Percy, Edward and Stanley. His enemy is Diesel. He works on Thomas' branchline.