the scope is essentially a camera I think, and probably a better one than the zaku optics. If I recall, in the original MSG series you see Amuro has a sighting piece that he pulls down in order to get precise shots with his beam rifle. Infact I believe in one episode the Gundam's head is eather destroyed or the cameras damaged and he is forced to use his Gun's sight camera in order to see until he gets repairs.
They took the barrel shroud style and barrel change mechanics from an MG-42. The receiver is pretty generic, maybe a little AR-15 influenced.
As to the scope, especially in Minovskyland you'll need some powerful optics to cope with interference, with a wide range of options. Options there probably aren't room for in the Zaku head. While a Zaku wouldn't have a problem with general shooting without a scope, taking faster and more precise measurements would be easier with a dedicated optics suite for the rifle that doesn't worry as much about different angles of view amplifying the Minovsky effects.
Is a sniper beam rifle. The backpack is a power source/generator and the cable is used to power up the rifle. And this is canon. The design looks like a MG-42 somewhat, but the internals are totally different.
