Zachary Galifianakis goes by "Zach," Zachary Snyder goes by "Zack," and Zachary Efron goes by "Zac." Best I can tell, none is more correct than the others and is a matter of family or personal preference. Mets prospect Zachary Wheeler goes by "Zack," which is, therefore, how it should be spelled. His name is his name (language at link NSFW). However, several media outlets have struggled with the spelling of late:
His given name isn't "Zackary," so the mistake is somewhat understandable. Still, people should get it right. Here's Amazin' Avenue's Michael Donato with a useful tip for remembering that it's "Zack" and not "Zach":
fyi for all Mets fans (and writers) since he'll be coming up soon..Zack Wheeler with a K. Because he's a pitchers, and pitchers like Ks.— Michael Donato (@Ceetar) June 14, 2013
This has been Nitpicking With Amazin' Avenue.