Zischang was one of the all time great custom gun makers. As Mike mentioned, right there with Harry Pope, George C. Schoyen, and other greats. Zischang is probably one of the most well rounded custom gun makers, as his talents exceed Pope's for aesthetics. Pope made some fine barrels, but was never one to build beautiful guns, like Schoyen or Zischang did!
Your Ballard has features common to the #8 Union Hill, with it's loop lever and double set riggers, but I'd guess it didn't start life as a Union Hill prior to Zischang's custom work, as it doesn't have the rebated receiver of a Union Hill #8 or #9. The serial number and the Marlin Firearms Co. roll stamp make it a later Ballard, from likely around mid 1880's. There's a 50-50 chance the breechblock serial number doesn't match the receiver, and maybe also the wood. This would hurt the value of an average Ballard, but doesn't hurt the value of your Zischang Ballard at all! Having a gun built up by someone with his reputation is a huge premium over standard Ballards, so nobody will care what it started life as, or what parts went into it.
It's a stunning piece, and unless you stumbled into some person who was totally clueless, I doubt it came cheap. His name is enough to elevate a gun to a double price of a standard Ballard in similar condition.