You haven't deleted your EFI partition by any chance?
I think they are usually set about that size.
Are you able to post a screenshot of your partitions from Windows Disk Management or Gparted? That may help us understand what partitions you now have left.
That might be it. How do I restore it or rebuild it? With a flash drive?
Others may help once they can see what partitions you have and what is missing.
In the meantime, you could have a look at this thread:
Yes, you deleted your EFI partition. Since you created a new partition, you may try using os-prober to identify the Operating Systems on the machine and add them to grub or try Boot Repair...
Which method do you want me to try first?
os-prober
in recovery mode with root?
or
Boot Repair
How do I do this? Any guide?
I am rushing out the door, back in about an hour or so...
I have never tried os-prober, but can say Boot Repair has got me out of trouble once.
It is undoubtedly the boot partition.
Being FAT32 file system, that is the only Linux partition Windows can access. See the partition mapping of my Zorin installation below:
Yeah. I have a bad habit of doing stupid stuffs. But this is how I learn.
Lesson here: DO NOT TOUCH the 500 MB FAT32 that shows up randomly in Windows 10.
For sure. I just saved my butt. I'm back in Zorin OS.
How did you end up fixing it. Boot Repair or what?
In general, it is better not to meddle with the files in other OS unless you setup a shared data partition.
Boot Repair through Zorin OS Live boot on the flash drive. I saw it reinstall grub and linux-header-generic.
Thanks for confiring that. That info may help someone else one day. Good to hear you are back zorining again 
After I fixed it with boot-repair with live boot, I boot into ZorinOS safely. I checked with
sapphire@sapphire-X570-UD:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 223.6G 0 disk
├─sda1 8:1 0 1K 0 part
└─sda5 8:5 0 223.1G 0 part /
It looks wrong. Where is the EFI partition now?
Extra photos
Can you post a Gparted screenshot.
Your FAT32 EFI partition is on the first disk you show, not the second. But is only 100Mb.
You are dual-booting Windows, Yes?
Absolutely NOT. I know dual-boot is horrible when Windows 10 is on the same drive. That's why I put ZorinOS on its own SSD. It used to looks like @FrenchPress
's picture.
I remember when I tried to save as much space possible on a 7GB eMMC, I found that the boot partition could be as small as 100GB.
