. So, it is still possible for me to get a new Z visa in the United States for my next employer at the Chinese consulate with the residence permit from my last employer still inside my passport book?

how many monkeys can dance on the head of a pin?!

I personally would not take anything as sacrosanct regarding the Chinese consulate, whether in the US or their representative office in the HK SAR. Would you want to risk being stuck in the US, homeless and poor, because of a failure based on their "promises". One thing you should remember with chinese is that they are the most dishonest people in the world....trust them, I should coco......

but good luck either way.