The Senior Slam features the winners of the four major championships on the 2002 Champions Tour schedule. Zoeller, who earned his first career victory on the Champions Tour at the Senior PGA Championship in June, collected five birdies and no bogeys at the Lost Gold Course.
Zoeller came close to an eagle at the par-5 second after his second shot stopped within 10 feet of the hole. Zoeller's putt slid by the cup but he made the birdie coming back.
'I haven't played the course enough to know which greens are fast,' said Zoeller. 'I'm putting back up the hole into the mountain. I've got to think it's kind of slow. It kind of caught me off guard.'
Don Pooley, who won the U.S. Senior Open in a playoff over Tom Watson, birdied the first two holes but ran into trouble with a bogey at the sixth. He countered with a birdie at the very next hole and added another at the 10th to move to 3-under.
Pooley found trouble again with a double bogey at the par-3 11th but managed to respond with a birdie at the 13th to finish three shots back at 2-under-par 70 alongside Stewart Ginn.
Ginn, the winner of the Ford Senior Players Championship, had two birdies and one bogey on the front side to make the turn at minus-2. He bogeyed the 10th before catching fire with three straight birdies starting at the par-5 14th. Ginn then bogeyed the par-3 17th to finish in a tie for second.
Jim Thorpe, who made Superstition Mountain the site of his first major title on the Champions Tour at the Countrywide Tradition in April, struggled out of the gate with a bogey at the first and a double-bogey at the second. He recovered with six birdies and three bogeys the rest of the way for a round of even-par 72.
'I knew it when I woke up today,' said Thorpe. 'I just didn't have the feeling.'
All four competitors are making their first appearance at the Senior Slam.