The only diffs are the brand of SSD the OS is on, probably the brands of DVD and memory. The 2nd HDD is a different size, I think, and maybe a different brand.
I suppose I could just stick the SSD in and see. But I don't want to mess up this installation now that it is perfect.
You most likely can safely do so. Just ensure that you update and upgrade right after and check any drivers.
OK, thanks. No harm in trying, I guess. Does Zorin have the ability to clone the disk it is on? Is there a utility to do it? Could I do it in a Windows PC?
I would recommend using RescueZilla as the Easiest method.
But there are many methods.
Clonezilla got you covered, it can quite literally clone the contents of one drive to another
just plug both drives into the same PC, flash CloneZilla to a USB, and follow a guide somewhere on the Internet from there 
The already installed applications on Zorin Core like Disks and Gparted are capable of preforming such a job.
While the source disk is being used?
I got three partitions. Two say Filesystem and one says Extended Partition. Both claim the whole 119GB of the SSD.
Edit: OK, if I click on the physical drive in the left corner, then the 3 vertical dots on the right corner, I have an option to Create Disk Image.
I should move all of my larger junk to the HDD first.
Then, presumably, I plug in the other SSD and Restore the image to it. Format first? Couldn't hurt.
What if you didn't have enuf room? Could I store it on my NTFS HDD? Edit: It says I can. Might as well.
I don't know about using different size harddrives, but I cloned same size USB thumb drives and it works.
I cloned a Zorin OS installed onto a USB thumb drive on my lenovo T430 thinkpad. After I installing it, I used a free windows program called 'Active Disk Image Lite 11.0 - Freeware' to backup the USB to an image file (It can back it to a compressed image file to save space). Then a wrote that saved image onto a second USB drive (exactly same USB model & size) and it runs OK like the first USB does. So, yes you can clone Zorin install and run it. The Zorin install runs OK in all my other lenovo thinkpads (3 different models).
Just done a search and the best way is to put SSD in an enclosure:
Clonezilla is tricky - Disks creates an .img file backup but you might hit problems using that to fit on a smaller drive - another option would be to shrink you larger Linux installation to match the smaller one - but not sure if you could expand afterward.
Replace Ubuntu 18.04 with Zorin 16.1! (hopefully!)
You are doing fine there I see. But you should rather use the cog wheel for the partition(s) you want create an image for instead of the 3 vertical dots. The 3 vertical dots lets you image the total drive, while the cog wheel is for individual partitions.
As for space, I remembered that the application Disks (and also Gparted) creates an image of the total partition (instead of the present data). Which means you will have to reverse the same or bigger size partition which to restore to. Just like Dav suggests, but he used identical usb (with the same size).
I want to clone the entire drive, from one 120GB boot SSD to another 120GB SSD.
Don't know much about Linux partitioning. Seems odd compared to Windows.
Well then your first try was a better option. If the size is the same, I don't see why there should be a problem. If the drive is attached you can use the same application, and restore the image, the same way you saved it.
I'm not that familiar with windows partitioning. Never use it. I like how the ability Linux/ Gparted provides while resizing or adjusting a partition. Almost never encountered any problems. And if I did I just reformatted and started all over again, because you have the original image. So no harm or pain there. Its trial an error, once you get used to it, it'll be a very easy.
I once did try the same like you and it worked, even boot files and grub settings were copied and restored. So I was able to use data from one partition on a second drive.
Edit, after the restore you will have to run the update/upgrade because of the drivers on the second pc. Just like Aravisian suggests.
