The train starting with "z" is a direct special express passenger train, which is called "straight" for short. The letter Z is the abbreviation of "straight" in Chinese. All direct trains are operated across bureaus (not in a railway bureau).
All direct trains are operated across bureaus (not within a railway bureau). This kind of train appeared after the fifth speed increase on April 18, 2004. Although there were direct special trains in the past, they were all mixed in the number of express trains.
Generally speaking, Z is faster, because the car (25T and BSP) used by car Z can run at a maximum speed of 160km, and the maximum speed in actual operation is about 150-155, while the car (25K) used by car T has a speed limit of 140km, but some cars (T11, for example) also use 25T cars, T15,T202,T97,T99,T158,T27, Wait, the speed of these trains in actual operation is basically the same as that of Z trains on the same line. In fact, when the railway department formulates the train diagram (timetable), these T trains are also drawn according to the standard of Z trains.