Yes, you can change the extension of the export file from .imscc to .zip without problems. In fact you can even leave that .zip extension and then import it as a Canvas course export file. The expanded .zip file has a folder named "web_resources" that has the content within the Files area of your course, which should contain the image files. The "wiki_content" folder items are what was in the Pages area of a Canvas course. It is true that trying to open those .html pages directly will not replicate the experience of viewing those pages within a Canvas course, and that's because those pages are written to be opened within a Canvas course. That environmental assumption also affects the files that correspond to assignments, discussions, etc. I find opening up a Canvas course export file to be most helpful when I'm trying to find a specific file.
While Blackboard course export files can be imported into Canvas, it will be a challenge to find folks with the relevant Blackboard expertise in this community. I hope that our colleagues who do have that expertise will share it here.
