In the original blog post from ZM (see below), they stated they had 10M daily participants in Dec 2019, and 200M daily participants in Feb 2020 so even if they are saying the March number is 300M ‘daily participants’ and NOT ‘daily active users’ it is still the same metric they were using for the Dec and Feb updates i.e. a 30 fold increase in daily participants.
I believe they edited that blog post after they were alerted to saying 3000M USERS.
https://www.businessinsider.com/zoom-blog-post-daily-active-…
Denny Schlesinger