There are about 500,000 account of zoom were sold on dark web by hackers. Hackers sold each account for less than a penny and some accounts are given for free on the dark web by hackers.

These sold accounts were collected by hackers and theses accounts were those accounts that try to login their zoom account by their older data breaches. Whoever logged in successfully in this way then their account added into list.

Later these accounts were sold in pennies and some are offered for free to dark web by hackers.
Cybersecurity intelligence firm CYBLE informed bleeping computers about zoom accounts that were posted in Hackers forums on 1st of April 2020.

Later, Bleeping computers clarify that this is not because of breach of zoom. The reason of hacking is Documents stuffing attack. It is basically a technique used by hackers to hack the account from previous information or password leaks then hackers try these passwords on other social apps to check the reliability of this method. Whosoever shared his information, got effective by hackers and the numbers of people who get effective are more than half a million. This information included user Email, password, meetings ID and hosting key.
Zoom is not only effective or attacked by this method, also there are many other sites who got effective.
You need to be very careful to avoid your account from hackers. Try to use different passwords for different services, if you are using the same email and try to use difficult password including alphabets and numbers.