Networks undergo continuous changes to introduce new services and improve existing ones. Network change deployment involves carefully deciding when each change activity will be executed and who will be executing the change. This is a complex process because each service group has to plan its activities following a set of operational and technological constraints. Besides, multiple groups may be working on the same or dependent nodes at the same time, and they must co-ordinate their deployment plans. If they do not co-ordinate, conflicting change execution could result in unexpected impacts. Traditionally, change deployment has been a tedious and time-consuming task. To address this, we propose an innovative solution Zapper that aims for minimal human effort to coordinate the changes, minimal risk to service quality, and efficient plans to rapidly deploy the changes. Zapper maps change scheduling constraints into mathematical equations and then uses optimization algorithms to generate conflict-free change plans that satisfy all constraints across service groups. We have deployed Zapper at a large service provider and it is being used regularly by the network operations teams for more than two years to schedule over 4.5 million change activities.