The ChromeOS Zoom App is no longer available. Please read this article to use Zoom for Chrome PWA (Progressive Web App): https://support.zoom.us/hc/en-us/articles/4403638230925-Using-Zoom-for-Chrome-PWA
If you need more information, you can read this article: https://blog.zoom.us/how-to-use-zoom-on-a-chromebook/