Loading Snow Leopard OS 1.6 to Second Partition of Newer Mac
On a 2017 iMac I split the hard drive into two partitions. High Sierra OS 10.13 is loaded on the first partition, and I would like to load Snow Leopard OS 10.6 to the second partition. So I inserted a USB flash drive that has a bootable copy of Snow Leopard. I tested it on an older machine to be sure that it works.
I then opened Disk Utility, which recognized the USB drive as bootable. So I changed the startup disk to the USB drive.
But when I reboot, the Mac stalls at the grey loading screen with the Apple. It refuses to start from the USB drive.
How can I get Snow Leopard OS 10.6 installed on the second partition?
iMac Pro