When you boot your machine GRUB appears and lets you choose which system shall boot.
Leave Secure Boot disabled (Windows nevertheless boots in secure mode) - but change the boot mode back to UEFI. Afterwards install Windows and then RHEL 7.4, but this time choose "manual configuring" in Anaconda installer and select the ext4 partition for RHEL you had created before.
Windows 10 vs Redhat 7
Windows 7 vs rehat 7
