Zbrush has huge system requirements, resulting in frequent crashes if your system is not properly maintained.
I use Iolo System Mechanic, there are other PC maintainence programs, including the Windows default programs for disk cleanup and defragmentation.
If I don’t run a complete cleanup diagnostic at LEAST once a week, more often if I’ve been working hot and heavy with lots of file saving and deleting, my computer starts running sluggishly and Zbrush crashes in the midst of important work.
So, keep your machine running smooth by doing frequent maintainence, and hopefully avoid crashes at inopportune moments.
~Traveler in Thyme