How to create a zip file of multiple images
Like other archives, ZIP files are data "containers", they store one or more files in the compressed form. You may only upload images using this form. If you upload any other file type your upload will fail.
Create a zip file on Windows
Add your jpg images to a folder, then right click on the folder and select "Send to > Compressed (zipped) folder". You will end up with both the original and a zipped copy.
Create a zip file on a Mac
Add your jpg images to a file, then just CTRL-click on the file and select "Create Archive". You will also find the option in the File menu. Either way, you will end up with both the original and a zipped archive copy..