Are you referring to the National Zoo?
"All Smithsonian museums in Washington, D.C., including the National Zoo, and in New York City continue to be closed to support the effort to contain the spread of COVID-19. All in-person public programs, events, and tours are canceled through July 1. We are not announcing a re-opening date at this time and will provide updates on a regular and as needed basis."
Source:
https://www.si.edu/museums
Check there for any changes or updates.