He switched from Burundi to represent Qatar and adopted a new name Sultan Khamis Zaman while competing for them. He ran under his new name and country at the 2004 Summer Olympics. He finished eighth in the short race at the 2004 IAAF World Cross Country Championships and won a team silver medal with Qatar.
He changed his allegiance again in 2010, returning to Burundi, and changed back to compete under his birth name, Onèsphore Nkunzimana.[1] He won the Eurocross for a third time in February 2010.[2]