While installing Zorin according to thr directions, I arrived at the place where you have to install alongside another OS or etc... I selected alongside another OS, partitioned some space for it on one of my drives, and installed Zorin.
I cant seem to find a way to log back in to windows instead of Zorin. I've been tk the BIOS, at thr boot menu, I select any of my three drives, and windows does not show up.
Are you booting both in EFI mode? Legacy? One of each?
Have you tried Boot Repair?
I understand that the article suggests if Ubuntu won't boot- but it can still apply to your situation. The Boot needs to run OS Prober.
(joke) who needs windows after using zorin os 
I dont want to lose all my stuff
You should be able to access your "stuff" in the file explorer window, choose other on the left side and you will see the windows partition as an option (listed by the size in gb, maybe the partition name). Choose it and you can go to users[user-name]\desktop or documents or pictures and copy everything over before removing windows altogether (last part optional).
Okay so to be more clear, I installed zorin on an entirely different SSD than windows was installed.
When I take out the zorin SSD entirely, and boot the windows SSD from the bios, black screen only with a flashing cursor
Weird issue you have, cause i did the same and have none issue
1st drive: Samsung 980 1TB nvme (Windows 10 installation)
2nd drive: Western Digital Blue M.2. 1TB (Zorin OS 16 installation)
3rd drive: Samsung 870 2TB (ntfs drive, used for downloads, games and programs)
I disabled secure boot in the bios and changed the boot order so linux will fire up first. Did you change anything else in the bios ?
Does the WIndows SSD have an EFI partition?
So I connected the original windows SSD to another PC I have, it shows up in Disk Management, and on my new Zorin OS it shows up in Disks, but not in any file explorers.
The drive may show up with its files; but it is the Bootloader that needs to see it in order to boot.
If installed on separate disks, both need to have an EFI partition at the Beginning of the disk for the Bootloader (usually 512mbs in size or less).
Okay so the EFI Partition is what talks to the bootloader and lets it knows it's here. If that is not present for some reason how do I get it back?
You can use a Partition Manager to add the partition. Gparted in Zorin OS and I am not sure what they call it in Windows but knowing Windows naming conventions, probably "Partition Manager."
Screenshots would help greatly. It's not that we don't understand, but it would be easier to point the issue out to you if we are looking at the same thing. Sometimes when people don't know what they are looking for or understand the ramifications, they tend not to describe things or barely mention them.
The windows efi should exist, the Zorin efi should exist. Both are required to boot their respective os. If you dual booted with one efi it would narrow it down and give you the option at boot without modifying the boot order. I do understand how and why you'd go the other direction. But deciding by boot order does require individual efi partitions for each os installed.