The linked instructions from IT's FOSS are not particularly suitable for creating a dual boot on two separate drives.
They are written for a installation on the same drive.
The safest way to have Windows and Linux on one computer is to install them on separate drives (each OS with its own bootloader partition) and select the respective operating system via the BIOS at startup. If you don't switch between the two systems very often, this is the simplest and safest method.
It is not a real Dualboot but you avoid security risks with os-prober.
by the way is it safe having windows 10 and linux? ik windows 10 support ended but I at least i have a good anti-virus and I will only download trusted .exe file. And also should I encrypt my linux during zorin os installation before dual-booting just in-case or bad idea?
Well .isos aren't usually available, because Windows 10 for existing Windows users need to use Microsoft's Media Creation tool which creates a bootable USB. That is why I suggested you use Internet Archive. Besides, this forum is not a site for storing .isos.