He could've been unexplored like he is in this game. Of course I wasn't involved in deep competitive play or study back then so I wouldn't have known. In this game people didn't explore him.
They said his dmg output was bad... He can match Hayate almost every damn time. I've proven this.
They said he gets no guaranteed damage. He has set ups, be they sometimes unpractical, they exist. IN FACT his BT stun game is probably the best in the business... he just has no way to get you into BT.
Lets not forget that his 6T might not be the best but I does set you into a mix-up being pp~strings, one of those giving you guaranteed gatling kicks that go all the way through until the last hit... which is a 50/50 that opens up your opponent on NH, the alternative = his PP6K~ 50/50 and the best part is you don't even have to do all of the mix-ups and 50/50 after the pp. You can pp2(duck)T or pp4T putting you into his muay thai clinch grab where he can gamble 3 knees for good damage or push them away at square one giving him a free deep stun opportunity from 9K (guaranteed).
He lacks good defensive tools though and while duck is good, it's kind of gimmicky on evasion. He's pretty safe where it counts though. For what it's worth as well, he has a guaranteed CB off of the BT setups but it's far too situational to be considered in his regular play. It's very viable for Ayane though. It requires two guesses, but the CB itself gets guaranteed off the sit down.
I won't go farther than this but, all I'm saying is without someone inspired behind the character you're probably not going to find many people taking that character to its limits when they have so much potential. Most people are still using post CB 3P+K2, duck PP4, sway Blanka Ball like it's the best damage set up he's got.
Who knows maybe Zack had some godlike tech in the last game that no one explored. I doubt it honestly but with the amount of stuff I've discovered in this game that it seems like no one even tried to find (or really share for that matter), I wouldn't be surprised if Zack had SOMETHING that no one knew about that made him better than all of the characters in that game...
But I digress because... once again, I honestly doubt it.