New York's attorney general has written to the firm raising concerns over its ability to cope with the rise in users.
Zoom is now being used by millions of people for work and leisure, as lockdowns are imposed in many countries.
But its data security and privacy measures have been questioned.
The letter from the office of New York Attorney General Letitia James asked Zoom whether it had reviewed its security measures since its popularity surged. It also pointed out that in the past the app had been slow to address issues.