Zamkovoy earned a 16-11 decision over U.S. welterweight Errol Spence in the quarterfinals after Spence was given a second chance by Olympic tournament officials.
Spence lost in the second round to an Indian boxer but was reinstated after a study of the video showed his opponent had held him at least nine times in the second round. That should have led to enough penalty points to make Spence a winner.
There was no getting round the loss to the Russian, however, who advanced with a solid victory that set up a welterweight semifinal bout on Friday with Serik Sapiyev of Kazakhstan.
The other welterweight semifinal will send Taras Shelestyuk of Ukraine against Britain's Freddie Evans.
The light-flyweight division also got down to the semifinals Tuesday and what should be a good match was set up between a Cuban and Irish fighter.
Robeisy Ramirez Carranzana of Cuba defeated Andrew Selby of Britain 16-11 and will now meet Ireland's Michael Conlan, who won a 22-18 slugfest with France's Nordine Ouhaali.
Russia's Misha Aloian will face Tugstsogt Nyambayar of Mongolia in the other semifinal.
All of Tuesday's winners are assured a medal of some sort since the semifinal losers receive a bronze.
While the American men will not be receiving any boxing medals in the London Games, U.S. women will be getting two.
In the first women's boxing tournament in Olympic history, American Marlen Esparza will meet China's Ren Cancan in Wednesday's lightweight semifinals and Claressa Shields of the United States will take on Marina Volnova of Kazakhstan in the semifinals of the middleweight division.