Complex sentence: CD drives and many early DVD drives stored data with constant linear velocity, so that the data rate remained the same regardless of the position of the optical head; however, modern DVD drives use Zoned Constant Linear Velocity with different data rates in different zones.
Split into simpler sentences: CD drives and many early DVD drives stored data with constant linear velocity, so that the data rate remained the same regardless of the position of the optical head. Modern DVD drives use Zoned Constant Linear Velocity with different data rates in different zones.