I think my ultimate fix was changing the Zwift resolution to the lowest setting. Haven’t had any crash for almost 2 weeks yet. I haven’t had Zwift crash so much until macOS was upgraded. I didn’t have any crashes last winter. Only since I’ve upgraded to Sierra & the 1 before that did I had my laptop crash so much, even using other apps in the laptop.
There are other solutions that I’ve read in the internet, ie disabling the auto-switching on power-save, and installing gfxCardStatus (to display which graphics card is being used at any moment in time). Note: auto-switching is switch to On again on a reboot, so be mindful of it. Although, I’m not sure if this does the fix for me.
Good luck and hope this works for you too. Ride ON!