Why get a z visa before leaving your home country. Chinese embassies in foreign countries rarely issue work visas, with the exception of HK. Even if you have all the right documentation they can still deny you. It's much easier to enter the country on a tourist visa say for 30 or 60 days and then the school or business can switch it over when you arrive. I'm from Canada and tried to get a Z visa before leaving and it was such a hassel I ended up with everything I needed but they still wouldn't issue me the work(Z) visa so I left on a tourist visa, met with the school gave my passport and in like 10 days I had a work visa and residency permit. Another good way if you want to stay in China for a long time with is go through Hong Kong. It's much easier to enter mainland through HK. Can even get 1 year multiple entry business visas from alomst any hotel or travel agency!

good luck