I'm trying to figure out what acoustic this is. This is Zack Williams from 'The Lone Bellow.' Can't seem to identify it. Thoughts?

That's the best pic I could find. That's why I was having trouble identifying it myself.
That could be an older "Guild" slope shoulder, but without more info its my best guess. Cheers
Custom shop Martin would be my guess

Dallas Green of City and Colour plays a similar Martin which I know for a fact is a custom shop. Dreadnaught slope shoulder body, 12 fret body, slotted headstock, flowerpot inlay, shade top finish