President Zuma has arrived in the Seychelles to help broker a deal in a second round of talks between Madagascar's president and the man he ousted.
Madagascar has been mired in political crisis since Andry Rajoelina toppled Marc Ravalomanana in March 2009 with the army's support.
"South African President Jacob Zuma has arrived on the Seychelles," a government official said on Wednesday.
Both Rajoelina and Ravalomanana were already on the main Seychelles island of Mahe, where they are expected to meet face to face later on Wednesday.
The rivals on Tuesday met separately with Seychelles as President James Michel, who told them "the return of stability" to Madagascar is crucial for the wider region.
"It is my hope ... we can together reach a consensus that will establish a lasting solution for peace," Michel said in a statement on Tuesday.
The first one-on-one meeting between the rivals ended without a resolution on July 25 at an exclusive resort on Desroches, a private Seychelles island.
The 15-nation Southern African Development Community, which mediated the talks, extended a deadline to August 16 for the rivals to settle their differences.
Since then, the Indian Ocean island has announced the first round of long-awaited elections will take place on May 8 next year.
Although the two last year signed a roadmap toward elections, the deal has yet to be fully implemented.
The main point of contention is Ravalomanana's return to his country. Exiled in South Africa for the past three years, he wants to be cleared for the 2013 polls.