First of all, you need to get some background about the booting process. Old motherboard firmware with a BIOS program loaded use a specific sector in a disk to start from. That will contain the information for a second step etc. At one point it gets to the windows bootloader and you can edit that with EasyBCD.
Modern AMD/Intel motherboards no longer have a BIOS program in their firmware. They have an UEFI program. EFI looks for a specific partition (not a sector) and starts the loader from there. This is also where you can put a loader for your OS.
That changes the sequence of things.
Old:
- Firmware boots. Have saved setting to select a specific drive.
- Boot sector is read from a drive (basically a very small program).
- Boot sector program runs and usually loads a bigger program (lets call it bootload2)
- Bootloader 2 starts the OS (e.g. windows, or Linux, or ...)
Now you could insert a different program at point 3, then you get
- Firmware boots. Have saved setting to select a specific drive.
- Boot sector is read from a drive (basically a very small program).
- Boot selector program loads (e.g. GRUB).
Depending on your choice grub then loads the bootloader2 which runs windows, or GRUB loads something else which runs Linux (or any other OS).
Now it is going to get more complicated.
The thing a generically called bootloader2 usually just loads windows, but it can also be tweaked. THis is where your EASYBSD comes in.
Abandoning this an moving to EFI (your current setup)
- Firmware boots. Firmload looks at the drives and find the ESP (Efi System Partition).
- If a file is set in the 'BIOS' *EFI loads the bootloader (e.g. bootX64.efi) on the filesystem and loads that.
- BootX64.efi loads windows.
- Windows starts up in EFI mode.
You can have multiple loaders on the ESP partition. Given a good motherboard you might even be able to select one of these when it powers up.
Alternatively you could have a EFI program which does not just load the OS, but which was which OS to boots and then transfers control to the right bootloader.
OK, plenty background. Now to one of your question.
And if I change my Boot mode , do I have to reinstall my windows?
Many EFI firmware have CSM (compatability shims). This is sometimes calls legacy mode.
If you enable this it will try to boot in the old way. That means that you will have to add a bootsectors. You will need the old bootloaders. And windows installs different parts of itself depending on how you booted. You you end up with reinstalling windows.
So "do I have to reinstall my windows" is:Yes, you end up reinstalling.
As yo how to actually solve this: Leave the firmware on EFI only. That greatly simplifies things. Next find an EFI loader for Zoron OS, the best start point I found for this is this post on our sister site. https://askubuntu.com/questions/436096/uefi-and-reserved-bios-boot-area
*Actually BIOS is a wrong name. There is neither a BIOS program present, nor do you store things in a BIOS in the classic setup. It gets stored elsewhere and read by the BIOS. But lets keep things simplified here.