As explained in the article NgZone (zone.js) is a separate mechanisms from change detection. It’s only used to trigger change detection by calling
ApplicationRef.tick(). If there’s no zone you can manually trigger change detection by injecting
ApplicationRef and calling
tick() method to run change detection.
digest part, I think you should read Angular’s $digest is reborn in the newer version of Angular. I would also recommend reading all of the articles listed in These 5 articles will make you an Angular Change Detection expert.