How are these bills now worthless? I can't go to Zimbabwe today and get 100 trillion dollars (2.6 billion USD) from the currency that they printed that is supposed to be worth that amount?
Per Wikipedia: "The final redenomination produced the "fourth dollar" (ZWL), which was worth 10^25 ZWD (first dollars)."
The ZWL itself was subsequently largely abandoned, too. I believe you'd have more luck transacting in foreign currencies.