the currency would have been useless outside of their borders at the time so there really wouldnt have been a value. They were clearly having to pay inflated rates for anything of value though.
Why do you keep insisting that Polish currency had no worth? The inflated monetary price of goods during war time does not mean currency has no value. Currency conversion rates change on a daily basis and are contingent on global behaviors. To say the zloty was worthless during the German occupation isn't accurate.
There is not going to be a correct answer when you're asking about the equivalent monetary value of the past to today's US dollar, and especially comparing the USD to a currency in a country that is occupied with their currency is being taken over by another.
However, JayfromtheBay gives the most correct answer here. In 1940 the Nazi's set up a new bank in Poland and fixed the exchange rate at 1 Reichsmark = 2 zloty. 't the same year, 1 dollar = 2.50 Reichsmark. So, 2000 zloty would = 400 USD, about the same as what he said.
What that amount would buy in 1939 Warsaw is a whole other question.