Zack the Diesel Engine

Zack as his name implies, is a sinister diesel shunter and the last diesel engine to arrive on Sodor who originates from the Other Railway. In the television series, Zack is a permanent resident of Sodor.

Thomas & Friends
Zack first arrived on Sodor in the same way as Diesel did in and was sent away for telling lies about Bill and Ben, but returned when Thomas and Percy needed help at the clay pits. Zack proved to be as bad as ever and was sent away for good after shunting some trucks of china clay into the Mines, but he somehow mysteriously sneaked back to give Bill and Ben advice, taunt Glynn about not being able to run on the railway anymore of Thomas's power on the Sodor. It is possible that these events happened during Samson's Dino Delivery and also returned at some point with exploding Bombs from the Mainland.

When Henry was derailed by some trucks, Thomas and James were brought back as a last resort to do his goods work, but his attempt to prove his worth resulted in him Not being able to take it and it made Zack and he was sent back to the Mainland yet again and back to Sodor.