I imagine that a gun suitable for ZZs would be fairly closely modelled on the principles of the old live pigeon guns - built solidly and heavily for 1 1/4 loads, flat file cut ribs, tight chokes, long barrels, semi-pistol grips and high combs to get high patterns for rising birds (livelier stocking), perfectly fitted for swift, sure mount etc. ZZs are, after all, supposed to simulate live pigeons...
RG