He also said that Heim had travelled from Puerto Montt to the resort town of San Carlos de Bariloche in southwestern Argentina "50 times in one year".
The two towns are 350km apart and are separated by the Andes mountain range.
Zuroff believes that Heim is hiding somewhere between the two towns.
Heim's children have never claimed a bank account believed to contain $1.6 million and other investments in his name. To do that, they would have to produce proof that he is dead.
Heim, an Austrian national who would now be 94, is wanted for allegedly killing hundreds of people in concentration camps during the second world war.
Most of the victims died during medical experiments, including performing operations without anesthesia and injecting petrol directly into their hearts.