I don´t know but I think that If I would have to compare my sound it would be somthing like Zakk´s. I use BOSS SD1 and play it through Marshall AVT100. Reason why it´s pretty close (I think) is ´cause I use dist on dist and like while soloin´ to turn on wah and have it around the middle position. I never do constant WAHWAHWAHWAH, I mostly use it a little bit especially when playn´ fast and than when bending I usualy go whole the way.

I found out that through doing this, the pick sound gets (when pickin´ fast) sticks out pretty much and I like it.

Of course Petrucci´s and Vai´s sound are probably the greatest out there but who can afford 50.000$ just for guitar equipment, lol.