Complex sentence: There are no precise dates for when the Gen Z cohort starts or ends; demographers and researchers typically use starting birth years that range from the mid- 1990s to early 2000s, and as of yet there is little consensus about ending birth years.
Split into simpler sentences: There are no precise dates for when the Gen Z cohort starts or ends; demographers and researchers generally start birth years in the early 2000s. Some start the birth years ranging from the mid- 1990s to early 2000s, and as of yet there is little consensus about ending birth years.