Zone defense

Zone defenses are common in international, college, and youth competition. In the National Basketball Association, zone defenses were prohibited until the 2001--2002 season, and most teams do not use them as a primary defensive strategy. The NBA has a defensive three-second violation rule, which makes it more difficult for teams to play zone, since such defenses usually position a player in the middle of the key to stop penetration. The Dallas Mavericks under coach Rick Carlisle are an example of an NBA team that have regularly used zone defenses.

Question: is it illegal to play zone in the nba
Answer: no