The collected works of Ernst Zermelo, one of the founders of axiomatic set theory, provide a comprehensive insight into his significant contributions to mathematics. This second edition includes Zermelo's works on calculus of variations, applied mathematics, and physics. The collection is of interest not only to mathematicians but also to professionals in engineering and IT who wish to understand the foundations and developments in these disciplines. The publication is available in two volumes, with the original texts presented in their respective languages alongside an English translation on facing pages. Each paper is accompanied by an introductory note from a recognized expert, explaining the historical context, motivation, and impact of the works. This careful presentation makes the collected works a valuable resource for both students and professionals alike.