"This block was the result of a communication error between Zoom’s domain registrar, Markmonitor, and GoDaddy Registry, which resulted in GoDaddy Registry mistakenly shutting down zoom.us domain. "
MarkMonitor is a registrar (one of many). GoDaddy Registry is the .us registry operator (the only one); they actually operate the TLD on behalf of the government. In this capacity they are not operating as another registrar, but as the TLD operator.