No...he was still a joke character, it was just more subtle. It's like a weird, inverse effect of Paul Phoenix post Tekken 3 where he was a badass before but a joke after, Zack was a joke character from the start, but found himself in the right spots to win the tournament(especially 2 since he is actually the champion there despite Ryu defeating Bankotsubo) and getting rich enough to not only buy one island but two.
And again, he is working for HELENA DOUGLAS! Who the fuck cares after being a joke when he saved her damn life and she pretty much enlisted him as the voice of DOA and most likely her confidant. Besides he still has a better fate than Brad Wong...