Some users with Mac OSX 10.11 and OSX 10.12 who have NVIDIA GeForce 600 series GPUs will occasionally crash while running Zwift. This is due to a bug in Apple's driver for those cards in 10.11 and 10.12. Affected computers include many iMacs from 2012 as well as a few Macbook Pros from the same time range.
While we can't fix this issue on our end, you can download the fixed driver direct from NVIDIA for your version of OSX using the links below:
If you're unable to install the driver for your OS, see this forum thread for discussion on why this may be happening.