The opening-round co-leaders both put together three-hole birdie runs on the back nine Thursday in 6-under 66s at the year's final major on the Champions Tour.
Zoeller got his run earlier in his round than Ahern, who was among one of the last groups to finish play first round in the senior event.
Ahern finished his round with a flourish, with birdies on the final three holes.
Ahern said he knew that Zoeller had finished at 6 under well ahead of him, but he was just ``taking it shot by shot'' as he found the right rhythm for the final three holes on the 7,200-yard Reserve Vineyards Golf Club.
He landed a perfect 8-iron just 15 feet from the cup on the difficult approach to the 17th green, tucked behind trees along a creek that cost many other players penalty strokes. And on the final hole, he crushed a 5-wood 245 yards on his approach to reach the back fringe of the green and narrowly missed an eagle putt.
He said he has been pushing himself to finish in the top 30 on the Champions Tour money list this year after winning the Music City Championship in June, only the third win in his pro career.
``It's a goal of mine,'' said Ahern, who has slipped from 24th to 35th over the past two months. ``But I'm trying not to get ahead of myself.''
Zoeller barely broke par on the front nine after bogeying the par-3 2nd, but he started the back nine with three straight birdies before adding two more on 15 and 16, both par-5s.
``Some people push the red button when they bogey one of the first couple of holes,'' Zoeller said. ``But heck, I was just getting started.''
Hale Irwin and Graham Marsh both finished with 67s, while six players - Wayne Levi, Tom Kite, Tom Watson, Bruce Fleisher, David Eger and Morris Hatalsky - were another stroke back at 68.
Irwin had his own string of three birdies, beginning on 15, but said he was unhappy with his overall play.
``I hit some very, very poor shots out there, but fortunately I got away with them,'' said Irwin, whose back problems have limited his play.
Irwin, the winningest senior with 37 tour victories, said his back bothered him again Thursday despite steady improvement in his score through a round that did not include a bogey.
``I hit enough nice putts to salvage a very good round,'' Irwin said. ``On paper it looked very good.''
Marsh, only one of two players to birdie the slippery green on No. 2, also had three straight birdies on the second nine, beginning at 14.
``Everything went right for me,'' Marsh said. ``Even when I missed a green, I missed it in the right place.''
Defending champion Jim Thorpe led most of the round, topping the leaderboard at 3 under after the front nine, including an eagle 2 on the 337-yard 5th after he lofted a wedge right at the pin.
Thorpe had gone to 6 under by No. 15 before dropping back with a bogey and double-bogey after finding the water on both 16 and 17.
Thorpe's ball splashed into the water after he just nicked the stone wall rising from the pond guarding the green at No. 16, but he had to drop about 170 yards back to approach again. On the following hole, his tee shot found one of the long creeks that run through the center of the course and he took another penalty stroke.
Jack Nicklaus, a four-time winner of the final major on the Champions Tour, finished at even-par 72.
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