When opening an image within an archive, enable the containing folder to be browsable by the external image viewer so it can easily navigate through all the images in the archive without having to open each image individually. A freeware program call

I know that. I said "external" viewer and meant programs like xnview, irfanview, and Windows default viewer. When I double click on an image within your program it open up in xnview but then xnview's previous and next file functions do not work. When I do this within Zipeg, it unzips the folder and stores it in a cache somewhere and this cached folder and all the other pictures in that folder are immediately browseable with the previous and next file functions of xnview. I can understand why you might not want to make this the default behavior, but you could maybe make it an option. Maybe make it an option that varies by the size of the archive ie. only for archives less than 100Mb or something. Maybe ask us if we are sure we want to continue if the size is unwieldy and may cause a delay.
Thanks for your consideration and feedback.