I apologize that your question has been sitting out here for a while now without a response. While Canvas Quizzes can't be merged, all of the questions in the existing quizzes should also be available in question banks, most likely in a bank called "Unfiled Questions." You can create a new quiz that combines questions from both quizzes by drawing them from that bank, and How do I create a quiz by finding questions in a question bank? details the process.
I apologize that your question has been sitting out here for a while now without a response. While Canvas Quizzes can't be merged, all of the questions in the existing quizzes should also be available in question banks, most likely in a bank called "Unfiled Questions." You can create a new quiz that combines questions from both quizzes by drawing them from that bank, and How do I create a quiz by finding questions in a question bank? details the process.
