Get z visa for China ?

I am wondering if I can get the z visa with all papers from a Chinese school for teaching? I want to get it in Phnom Penh? I am in Vietnam now. I would have to wait for the paperwork from the school from China first. This could be up to six weeks. If I travel to Cambodia, can I get the visa in one day? Or, how many? How much would it cost me? multiple entry?
Thank you.