[hunter2_]

You say backend, but the frontend also has tons of overlap. The first time I saw RingCentral was after much Zoom experience, and I was thoroughly confused (based on nothing but the frontend) by the similarity until reading up about it. As a one-time invitee rather than a frequent user, RC was absurdly identical to Zoom other than the title bar and icon.

[Wheaties466]

Ring central has used zoom on the backend for a while even before zoom went public. But just recently they added a powered by zoom watermark. And yes the applications do look very similar but RC meetings hasn't changed the UI in the 3+ years i've been using it.