had this issue for so long, even with latest Zerotier 1.8.9 on Windows.
As soon as i start the Zerotier-Service the CPU will go up to 100% (from 20% before).
DNS will not work for about 30 seconds anymore. No web-browsing possible anymore. I am only connected to 3 Nodes. Back to normal after those 30 seconds.
Same on stopping but only max 12 seconds.
Intel Core i5-8265U.
I can reproduce that anytime. Shutdown, reboot, sleep. Manual stop and start service.
thanks for Zerotier!