The Charbonneau commission's spokesman has refused to confirm whether the former top-ranking municipal officials will be testifying this week.
Last week, Rosaire Sauriol, the executive vice-president of engineering firm Dessau, told the commission Zampino was "the most powerful man in Montreal" while he acted as president of the city's executive committee.
Sauriol alleged Zampino orchestrated a system of collusion that has been extensively described during witness testimony before the inquiry.
Zampino appeared in court alongside Paolo Catania and Bernard Trépanier this week on charges of fraud, breach of trust and conspiracy while dealing with the Faubourg Contrecoeur project.
Gérald Tremblay, however, has continued to deny any knowledge of corruption within his former party, Union Montréal.
The former mayor resigned from his position last November.