The discussion revolves around finding supplementary books for learning methods of solving differential equations beyond what is covered in Zill's textbook. Participants express that while Zill's book is comprehensive, it may not delve into advanced solution techniques, focusing instead on uniqueness, existence, and qualitative analysis. Suggestions for additional resources include various titles that cover different aspects of differential equations, such as boundary layer methods, complex variable methods, and numerical approaches. The importance of narrowing down specific interests—whether for random equations, applications, or theoretical exploration—is emphasized. Several recommended books include "Ordinary Differential Equations" by Edward L. Ince, "Elementary Differential Equations" by Earl D. Rainville, and "Differential Equations with Applications and Historical Notes" by George Simmons. Overall, the conversation highlights the need for targeted learning based on individual goals in the study of differential equations.