Tipster @letsgodigitalNL outed what appear to be official CAD renders for the upcoming OPPO Find X4 Pro. The leaked renders illustrate the "quad-curved" display, the under-screen front camera, and the rear display, next to the phone's quad primary camera.
https://www.notebookcheck.net/Leaked-OPPO-Find-X4-Pro-renders-showcase-peculiar-Yotaphone-esque-rear-display-under-display-selfie-cam-and-quad-curve-panel.586997.0.html