Tsitispas, who gave up a two-set lead to lose the Roland Garros final to Novak Djokovic last month, went down 3-6, 6-1, 6-3.
Despite winning the opening set on a tie-breaker, Zverev, the 2017 and 2018 Munich champion, bowed out 7-6 (7/5), 5-7, 3-6 after Ivashka of Belarus converted his first match point.
Australian Open 2021: Daniil Medvedev finally wins five setter, frustrated Karolina Pliskova knocked out
The win stretched Medvedev's winning streak to 17 matches, including his successful run to the title at the 2020 season-ending ATP Finals.
Injury scare for Novak Djokovic ahead of Australian Open as World No 1 plays through pain in Adelaide exhibition match
Television pictures showed a raw blister on the palm of his right hand, where he grips his racquet. Djokovic said it was painful, although it didn't appear to hamper his shot-making.
Top-seeded Djokovic lost four straight games and had to save a set point before beating Filip Krajinovic 7-6 (6), 6-3 in an all-Serbian match, and No. 2 Thiem nearly squandered a 5-1 lead in his 6-4, 7-5 win over Vitaliy Sachko of Ukraine.
The 33-year-old Serb has been the top-ranked player at the end of a season five times: in 2011, 2012, 2014, 2015 and 2018.
Italian Open 2020: Novak Djokovic, Rafael Nadal enter quarter-final; Simona Halep, Karolina Pliskova also through to last eight
Nadal proved too strong for 25th-ranked Lajovic, who had valiantly but vainly launched a fightback after trailing 4-0 in the second set to the Spaniard.
Italian Open 2020: Simona Halep extends winning streak to 11 matches; Novak Djokovic beats Filip Krajinovic
Halep, who is actually on an 11-0 run overall stretching back to February, recovered an early break in the opening set and then overpowered her 29th-ranked opponent the rest of the way.
Djokovic was supposed to play doubles with Filip Krajinovic at the Western & Southern Open, presumably simply to get some extra court time ahead of the US Open
Adria Tour: Novak Djokovic breaks down in tears after hosting Belgrade exhibition, Dominic Thiem wins leg
Dominic Thiem beat Serbian Filip Krajinovic 4-3, 2-4, 4-2 in the final of the first leg of the Adria Tour in Belgrade. Thiem remained 100% over the weekend.
Rotterdam Open 2020: Defending champion Gael Monfils beats Dan Evans in straight sets to advance to semi-finals
Monfils will meet Serb Filip Krajinovic or Russian seventh seed Andrey Rublev, while Spain’s Pablo Carreno Busta faces Canadian teenager Felix Auger-Aliassime in the other semi-final
Australian Open 2020: Roger Federer cruises into third round; Fabio Fognini emerges victorious after marathon five-setter
Checkout all the match results of the men's singles fixtures from the third day of the Australian Open 2020.
Davis Cup Finals 2019: Rafael Nadal rescues Spain to progress to semi-finals, heartbreak for Novak Djokovic's Serbia
Novak Djokovic played singles and doubles matches on Friday but couldn’t keep Serbia from losing to Russia 2-1 in the quarter-finals of the Davis Cup.
Japan Open 2019: Novak Djokovic advances to second round with easy win; Japanese wild card Taro Daniel stuns Borna Coric
Djokovic, alongside Filip Krajinovic, had been knocked out of the doubles by the fourth-seeded Mate Pavic and Bruno Soares on Monday
Japan Open 2019: Novak Djokovic returns to court after nursing shoulder injury, starts with doubles defeat
Earlier this month, Djokovic was forced to pull out of his US Open fourth-round clash with Stan Wawrinka due to a nagging injury in his left shoulder
Alexander Zverev's split from coach Ivan Lendl may not be total disaster that it seems on the surface
Zverev has looked passive, frustrated and clueless on the court for much of 2019. His forehand, which was supposed to transform into a weapon under Lendl’s tutelage didn't, neither his ability to tough out wins from adverse situations – which is the exact opposite of what most people expected to happen with Lendl by his side.
French Open 2019 men's singles round-up: Alexander Zverev struggles past Dusan Lajovic in five-setter; Novak Djokovic strolls into round four
It took Alexander Zverev all five sets again as he advanced into the fourth round of the French Open with a 6-4, 6-2, 4-6, 1-6, 6-2 victory over Serbian Dusan Lajovic
French Open 2019: Stefanos Tsitsipas downs stubborn Hugo Dellien in four sets to reach third round at Roland Garros
Sixth seed Stefanos Tsitsipas dug deep to reach the French Open third round on Wednesday with a tense four-set victory over plucky Bolivian Hugo Dellien.
Miami Open 2019: Roger Federer sets up quarter-final clash against Daniil Medvedev; Simona Halep makes light work of Venus Williams
Federer, however, stylishly weathered the storm to seal the win the 52nd of his career in Miami — and set up an intriguing last eight match with the highly-rated Medvedev
Indian Wells Open: Roger Federer, Rafael Nadal inch closer to potential semi-final clash with brisk fourth-round wins
Former champions Roger Federer and Rafael Nadal edged closer to a blockbuster semi-final showdown at the ATP Indian Wells Masters on Wednesday with brisk fourth-round wins.