If the computer crashes (not just Zwift crashing) you may have a hardware fault. That model does not have any easily replaceable components so you don’t have a way to swap out the memory or other bits. You can fairly easily reset the NVRAM and SMC but it’s not very likely to help.
Hi, @Marc_Pfenninger-4208 Welcome to the Forums! I’m Norman from Zwift. Sorry to hear about the crashes, taking a look at your computer specs, it looks like it should be able to run Zwift.
Most issues for crashes are the graphic drivers, it’s not as easy to make sure your graphic drivers are up-to-date on Mac but this article should be able to help with troubleshooting.
If this doesn’t help, it might be a good idea to check this article to learn how to send crash logs to the support team, that way we can determine the source of the issue and give you a hand with it.