Zoom's popularity has obviously grown substantially in the last few weeks. However, there have been numerous recent security issues with Zoom that have been found and discussed (i.e., https://www.wired.com/story/zoom-backlash-zero-days/).
These security issues aren't purely theoretical: Today I had a case where Zoom had been locally modified to deploy a man-in-the-middle attack. This was for a technical user on MacOS and were lucky that they noticed the certificate mismatch error.
The GCSB have updated their guidelines for the use of Zoom https://www.ncsc.govt.nz/newsroom/zoom-security-advice-for-public-servants/ but these guidelines possibly don't go far enough given that there are exploits out in the wild and potential root access.