And Djokovic approaches the world number 1 Rafael Nadal.
The Serb will only be 35 points behind Nadal when he wins his fourth Shanghai title.
Djokovic has seen a resurgence in recent months after returning from an injury earlier this year.
He retired last year due to an elbow injury from Wimbledon, which would put him out of action for the rest of the season.
After a fourth round at the Australian Open in 2018, he underwent a "small medical intervention" to solve the problem with his elbow.
Things did not improve at the French Open, losing to Marco Cecchinato in the quarter-finals.
The 31-year-old started an incredible tantrum after this defeat and said he could skip the grass field season.
But at Wimbledon, he dazzled back into top form, including an epic duel with Nadal in the semifinals, before defeating Kevin Anderson in the final.
He took this brilliant form into the hardcourt season and won the Cincinnati Masters before clinching a third US Open title.
Djokovic's victory over Zverev, who leads to the Shanghai Masters final, has extended his unbeaten run to 17 games and lost just once in the last 26 games since Wimbledon started.
To close the gap to Nadal, the 14-time Grand Slam champion has to pass either Federer or Borna Coric. This semi-final will take place this afternoon.
Given that Djokovic was only a few months ago in the ranking, he admits to be surprised that he has reached the world 2 so fast.
"I said after the US Open, when I came back with my coaches, we sat down and developed a long-term plan," said Djokovic.
"The surgery that I had earlier this year has somewhat hampered my game and it took me time to regain confidence and comfort.
"In early April, we came together again and we all agreed that the US Open was the place we wanted to reach.
"It was much earlier on the lawn where I had a great week at Queen's, won Wimbledon and after that I played some of my best tennis.
"I'm just trying to keep going, being dedicated and committed.
"It's a surprise to make it so early, I have to consider my plan, but I always believe in myself. I know that I can be the best in the world and beat someone on any surface every day."