Djokovic and Alcaraz, seeking their first Olympic gold medals, are on a collision course should they survive their next two assignments for a potential mouth-watering final clash.
Zverev would be happy to spoil their plans as he looks to become only the second man behind Andy Murray to defend a men's singles title.
Djokovic has been here before. In fact, he has reached the quarter-finals at the Olympic Games on three previous occasions and has yet to hang a gold medal around his neck.
Playing in the twilight of his unrivalled career, Djokovic is determined to add Olympic champion in front of his name. He already has a record 24 Grand Slams in his trophy case, including three on the Parisian clay at Stade Roland-Garros.
Djokovic had to work hard to win the tiebreaker in the first set but was in classic form in the second, winning five consecutive games to seal the victory to reach the last eight.
The 37-year-old will next face eighth seed Stefanos Tsitsipas of Greece for a shot at another semi-final appearance. Djokovic won the men's singles bronze medal on his debut in Beijing 2008.
Alcaraz was in devastating form as he continued his spectacular run at this first Olympics with a third-round 6-4, 6-2 rout of Roman Safiullin.
The four-time Grand Slam winner will face Tommy Paul of the United States, where he will be looking to continue his successful run at Stade Roland-Garros. The 21-year-old is fresh off his maiden French Open title from last month.
Reigning Olympic champion Zverev kept his title defence alive on Wednesday with a 7-5, 6-3 win over Australia's Alexei Popyrin.
