I was surprised that the Zimbabwe dollar wasn't higher up that list, so I did a little research and discovered that it hasn't been traded for quite a while, so there are no 'up-to-date' currency prices for it.
The most recent 'official-ish' value on the Z$ is $1.2 trillion = GB£1 (http://news.icm.ac.uk/business/ 12-trillion-zimbabwe-dollars-for-1/584/), giving a ZWD-USD value of Z$814 billion = US$1.

This doesn't count, Vietnam is Communist, and propaganda tells me that Communism fails, hard.