Zim Blood in the Streets, time to buy!
Putting my Tin Foil fedora on I'd speculate that TPTB turned their Wall Street computer algos to teach the ZimG government not to use gold to back their fiat. "You guys know why Saddam Hussain and Muammar Gaddafi now swims with the fishies."
Yes, it does seem like it could be a punitive measure in some way. There is no way that TPTB would be happy with the ZiG and would want it to fail. Wiping out the stockmarket would be a strong message.