Once we deliver the software to users, we’re not there to answer questions or solve problems when they occur. It should simply work without problems. When introducing the concept of Zero Defects, one trick used is the challenge that at the final test there should be “no questions, no issues”. If the testers would have even just one question to ask or find even just one issue, the test is to be aborted as failed. My experience is that in no time the quality of the deliveries improves dramatically.