Windows on one SSD, Zorin on another SSD

[littlekun]

@NickS

Normally you’d have both system boot managers in the same efi partition but you have them on separate drives.

It won't be an issue if you have them on separate drives.

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@rockman

Boot repair gave me this: GPT detected. Please create a BIOS-Boot partition (>1MB, unformatted filesystem, bios_grub flag). This can be performed via tools such as Gparted. Then try again.
Alternatively, you can retry after activating the [Separate /boot/efi partition:] option.

I guess your installation happened in UEFI gpt mode while your BIOS is in legacy mode. Otherwise there is no needed for the bios_grub partition.

Your Windows is installed under Legacy mode with MBR. And as Zorin is installed in GPT, it's not detecting the Windows boot entry. First boot to Windows and launch the msinfo tool, look for the information BIOS mode. If it's legacy then Windows drive probably have MBR partitioning which doesn't have/require an efi partition.

And from Zorin share your partion layouts for both the drives. You can take screenshots from the gparted tool and use the following command:

sudo fdisk -l

Once confirmed this the case of MBR and GPT mismatch then you may try converting Zorin's grub efi to MBR:

@Aravisian

To convert from EFI to MBR, you must boot on a LiveUSB. Once Booted, use Try Zorin, then open a terminal.
Run:
(Replace sdXn with actual root partition)
sudo mount /dev/sdXn /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo chroot /mnt

Install BIOS GRUB to MBR:
(Replace sdX with the actual drive id)
sudo grub-install --target=i386-pc /dev/sdX
Generate GRUB config:
sudo update-grub

Edit:
In your case sdXn=sdb2 and sdX=sdb