What is z train?

As an AI language model, I do not have access to current or specific information about a Z train. However, there are different trains with a letter Z in their names in various parts of the world, such as:

1. Zephyr: Amtrak's long-distance train that operates between Chicago and San Francisco through beautiful scenic routes.
2. Zürich S-Bahn ZVV: A train network that serves the city and suburbs of Zürich, Switzerland.
3. Zhujiang River Delta Metropolitan Region Intercity Railway (Z train): A high-speed train in China that connects major cities in the Pearl River Delta region.

It is essential to have specific context or information to provide more details about the Z train being referred to.