Integrating Zoom with default Calendar
Thank you for motivating me to actually share the Automator service I made for this! 
https://jonathanalland.com/quick-actions.html
Install the Open In Zoom service, then highlight a Zoom URL, right click, and select &quot;Open in Zoom&quot;. This has only been tested on OS X 10.9, but I see no reason it shouldn't work on modern macOS as well.
I created this by looking at the zoommtg:// protocol format, and then doing some find/replace magic in shell and Applescript. (I ideally should have used just one, but doing it in two steps was a tad easier, because shell is more powerful but I'm more comfortable in Applescript.)