https://en.wikipedia.org/wiki/LVG_E.I
Note that the image has a rearward firing Maxim gun & a forward firing Maxim gun (on a flexible mount), with no evidence as to how this would be synchronized with the prop.
If there was another forward firing gun, it isn’t visible.
LVG (Schneider) did develop a system which fired a machine gun through the hollow shaft of the prop, but all that I have found on this suggests that it was abandoned due to lubrication problems with the specially design Mercedes engine.