Have you seen the new notes and coins yet? So when you had ZMK 5000 now you have ZMW 5 (drop 3 zeros)! The Kwacha is subdivided into 100 Ngwee which can be found again in forms of coins. The Ngwee existed prior to the rebasing, but the value of the coin material was higher than its face value, so it had practically disappeared from the market.
Now, there is also a coin for 1 Kwacha.
If you have old notes you can use them until June 30th, 2013.
Today (January 3rd, 2013) , for example, the Bank of Zambia’s exchange rate will give you 5.2543 ZMW for 1 USD (mid rate).
This is what you can read now on Wikipedia: On 22 August 2012 the Bank of Zambia issued a press release stating that the changeover date for the rebased currency had been set as 1 January 2013. The new ISO code will be ZMW. Initial reaction to the move was positive. Razia Khan, head of Africa research at Standard Chartered commented saying, “The rebasing might be kwacha positive, to the extent that it is a continued commitment to low, and stable inflation”. On January 1, 2013 the new Zambian Kwacha was introduced at a rate of 1000 old kwacha = 1 new kwacha. Until June 30, 2013 the old notes will remain legal tender alongside the new kwacha notes.
(Wikipedia January 3rd, 2013)