You might also consider learning x86 assembly language, which you could do using in-line assembler in Visual Studio - although it's a larger instruction set than Z80, you would have the advantage of being able to use much better tools than would be available for the Z80.
I've also just remembered that the Keil 8051 and Arm tools have a simulator in the IDE - there are size-restricted versions of these available for free download from www.keil.com
