> If the Zilog engineers would have been free to design their own ISA I'm sure they would have been able to come up with a much more elegant design.

That's an interesting idea. They were previously part of the team that designed the 8080 so they must have been very familiar with the ISA and the design philosophy.

I'm sure they'd be able to come up with improvements but how much more elegant it would have been is hard to say.