I do not think that there is a way to do this easily.
I checked to see if there was a report that could be run in the account and I did not see anything that would show you the results from all of the quizzes setup in an instance.
I also checked out the Canvas API and I found this information about Retrieving quiz reports. However, this will generate results for a specific quiz instead of all the quizzes.
This might make a great feature request for future releases in Canvas. If you have not already submitted this idea, you can do that HERE.
Hopefully this helps!
Thanks, Colton, for your help! We were looking to use the quiz tool for our course surveys, as I see that many others have done so already. It would be nice to have a feature like this in the future to make this process less cumbersome.