The biggest update for in-game communication to date in Zwift has been the recently revamped messaging within the Zwift Mobile Link App (IOS/Android).
In game messages no longer appear and disappear on your Zwift screen, you’ll be able to see who said what and reply either to the group, or via direct message.
The global messaging works the same as in-game, so it’s global when not within an event and becomes group-only messaging if you’re riding as part of a group ride or race.
NOTE: As mentioned in the video. The Zwift Mobile Link app has to be open and in the foreground (on screen) to receive any messages. It doesn’t operate in the background like other messaging apps you may be familiar with.