It marks an increasingly turbulent start to the year for Djokovic following his in January, preventing his participation in the Australian Open, as well as the to Daniil Medvedev.
Djokovic defeated Grigor Dimitrov 6-2, 6-2, 6-3 in a third-round match Saturday.
But it demonstrated that Zverev clearly has an anger management problem and a very short fuse.