Hello,
We can most definitely get this project done, and very quickly depending on how you would like to proceed. We have our own IP that does almost exactly what you need this to do that was designed for ESL and ACT/SAT type tests. We can repackage this for you, add the few additional features we would need to meet the rest of your requirements (video/audio/pictures inserted into the quizzes), and have this working for you in around 1 week.
We can give you a demo of what we already have first to show that it already meets many of the requirements. And because you will be able to look at it, you will see that the quality is very high and that we can completely meet your needs because we have the proven skills to do so.
Also, if you would prefer, we could drastically reduce the cost of this project for you by making this a Software-as-a-Service project. We would charge a very low monthly fee, say, $50 USD a month, with all of the features you want along with customer service, updates, and additional features added in as you need going forward for a small extra fee increase (maybe an extra $10 a month per feature).
Please let us know how you would like to proceed and please contact us to discuss the details further. We are ready to begin on this project and can guarantee your satisfaction because this is in a domain we are already skilled at with proven results that we can show you immediately. We are very used to working in multiple time zones (our dev is American)