I have a problem on visa extension

I have lived and worked in China on a Z type for 2 years. At the end of June my contract expires and I am told mine will be changed to an L type. I start at a new position on 1 September in another province. I work up to 30 June and have flights to Australia on 2 July leaving no time to now fly to the new city. I need my Z type extended for 2 months but apparently this can only be done in the new province. So, back in Australia, how do I get the L one converted back to a Z one. My house is in Victoria, I am visiting relatives in Darwin and country NSW. I may also visit Brisbane - which would be easier to get to an embassy. I understand I can only extend in the state where I live. Does this mean 'live' as in 'visit' because I don't live in Australia any more. Does anyone have any ideas on what to do next?