Wayne,
I think you need to wait more than five minutes after his victory to declare him an unworthy winner. If this is his only major victory in his career, then you can try to make that argument, but he's younger than Tiger and has yet to peak.
It is a tradition in the Masters that someone you have never heard of gets atop the leaderboard on Friday, and after realizing where he is and that he doesn't belong there, chokes himself to oblivion. Zach took the lead on Friday, hit it a few feet away on 16, three jacked it, then proceeded to bogey 17 and 18. But he didn't disappear, he had the mental toughness to come back from that and wrote himself a different history on 16, 17, and 18 this year. You gotta give the guy a little credit, he shot 69 today, won at ANGC from behind the lead group and behind Tiger, and today the conditions and greens were much more receptive to scoring so you can't argue he just outlasted everyone today when birdies and eagles were flying all over the place!
Don't overlook the fact he was #56 on the world rankings entering the tournament, so its not like he's a Van De Velde coming out of nowhere. If he wins a US Open, British Open or PGA in the next few years, will that vindicate him, or will you feel the setup of that course is flawed and created another unworthy winner? If he went on to win several more majors, would you revisit your assessment of the setup of ANGC this week if it turns out in hindsight to have produced a most worthy winner after all? I mean, a multiple major winner has to have a first major somewhere, and not everyone is Tiger where you wonder "how many is he going to win?" or Mickelson where you wonder "is the guy going to go down in history as the best non-major winner in history?"
Maybe its just my state pride talking, but care to make a gentleman's bet that Zach Johnson never wins another major? I think he's got a very good game for say the US Open since he keeps it in the fairway and plays the percentages. Now that's won once, that'll only help him next time he's in contention.
And it does prove that you don't need to be as long as Tiger or Phil to win at Augusta. I played a couple times with Zach around 2000 or so and I was outdriving him a bit. So I guess I must have the length to play ANGC from the Masters tees. Just not the accuracy, consistency, short game or putting
Honestly though, if you told me he'd win the Masters someday, or even that he'd be capable of playing the tour well enough to keep a card, I'd have been willing to bet a lot against it. Not because he wasn't long enough but because he just wasn't good enough. He's obviously got a LOT better since then, so he may still have more room for improvement.