You can combine two or more quizzes using the Teleport feature. Here is a video explaining how it works:
You’ll find it in the Quizizz Creator, and its just 3 simple steps:
1. Search for relevant quizzes
2. Find the question(s) you want
3. Hit the little red button to add it to your Quizizz!
Now you can combine your private quizzes as well using the Teleport feature. You can search for them by checking your "include only my quizzes" box under the search.