Thank you for answer and information. So I guess that first Z-machine interpreters are capable to run seemlessly on 8-bit computers. I think that some later generations of Z-machine can do this as well.
As I said, Professional Adventure Writer and Quill and some other systems (DAAD for example) are used widely by adventure authors (for example Gareth Pitchford and other friends from the Facebook group). They are equipped with all important functionality, including variables, messages, actions, vocabulary, rooms and items.
They offer native functions, designed to work on these computers. Inform 6 + PunyInform library as a late generation of Z-machine requires adaptation - I guess.
This is a different thing to adapt the 16-bit system (like later generation of Z-machine) to work with 8-bit, than designing a system especially for 8-bit system.
I don’t support 8-bit myself, as I’m only the ADL, AdvSys games author. 
If I were into 8-bit, I would try PAW or Quill (or DAAD), either is available for Commodore 64. For now I have too small knowledge about these systems. If I were into new popular system, I would try Inform 6.
I like learning various authoring-systems in general.