I'm still not a native English speaker, but a Google search shows that non-paying customers are people who don't pay their bills, which is not the same thing as users who don't have bills to pay.
Also as I wrote, Zoom was thinking of selling E2E encryption as a payed feature, that's why the distinction really matters (I would happily pay for it if that would give me a strong assurance that I just don't have so far).
I don't think I'd happily pay for Zoom, regardless of their encryption promises. I've personally struggled more with zoom call quality issues and hardware conflicts than I have with any other video conference provider.
Also anecdotally, I hear the opposite from every single person I know. Zoom has been the video conferencing system that works the best. Have you ever used Go2Meeting, WebEx, Teams? Constant struggles with those applications for me, my friends, and my co-workers.
You really have to use Teams every day to appreciate just how buggy it is on all three platforms. I used slack video for remote standups for a year or so and aside from the odd little hiccup it was boringly stable. Teams fails at least once a week.
Non-paying customers can mean either customers who are delinquent in paying their bills, or customers that are using the service for free with permission.
Also as I wrote, Zoom was thinking of selling E2E encryption as a payed feature, that's why the distinction really matters (I would happily pay for it if that would give me a strong assurance that I just don't have so far).