This book presents a methodology for developing city-scale greenhouse gas and air pollutant emission inventories, and a synergistic analysis framework for achieving "dual attainments" based on air quality objectives. The book illustrates the pathways and strategies for cities to reach "dual attainments" using Zhengzhou, Shijiazhuang, and Huzhou as typical cases. The authors emphasize that "dual attainments" requires a comprehensive approach beyond end-of-pipe control measure?moreover, deep structural adjustments in energy, industry, and transportation sectors are essential. In particular, the green transformation of energy and the elimination of outdated production capacity can have a significant synergistic emission reduction effect and should be prioritized in decision-making. The methodological framework, analysis cases, and policy recommendations provided in this book are intended to enhance readers' understanding of "dual attainments" theory, equip them with effective methods, and enable the application of these strategies. Such an approach not only supports the advancement of sustainable development but also promotes harmonious coexistence between humanity and nature.