More than 200 law enforcement officers scoured the forest Friday for Zinkhan, some of the searchers crammed in the back of pickup trucks that crisscrossed dirt roads through dense woods.
Investigators said Zinkhan, 57, knows his way around the wilderness. But they reported no signs of the man and the Jeep was hauled away on a flatbed truck hours after the discovery.
Athens-Clarke County Police Capt. Clarence Holeman said the vehicle may have been left the day of the shootings.
Zinkhan also had a plane ticket to Amsterdam, and authorities in Europe and throughout the U.S. have been on the lookout.
"He's not the typical type of fugitive police have to deal with," said John Bankhead, a spokesman for the Georgia Bureau of Investigation.
FBI Agent Greg Jones said a signal from one of Zinkhan's cell phones helped police find the Jeep in Bogart, a rural town about 60 miles east of Atlanta. Bogart is about 10 miles west of Athens, where the professor lived and taught marketing courses at the University of Georgia.
Zinkhan's is accused of killing three people, including his wife Marie Bruce, in front of a theater in Athens. Also killed were two members of her community theater group, Ben Teague, 63, and Tom Tanner, 40, as they gathered for a reunion picnic.
Police hadn't previously revealed a motive, but Jones said Friday that interviews with friends and family indicate Bruce may have been preparing to file for divorce and the shooting likely stemmed from a domestic dispute between the couple.
Zinkhan's brother has said relatives have been working to help police and the FBI find him.