Ecosystem services refer to the various benefits humans derive from nature, including tangible material products and intangible regulatory services. Due to the heterogeneity of ecosystem spatial distribution structures and the complexity of ecological processes, enhancing one ecosystem service may potentially harm another. Therefore, a profound understanding of the interactions between ecosystem services, assessing the trade-offs (where one service's enhancement leads to another's decline) and synergies (where multiple services improve together), and identifying regional ecological priorities and dominant services are crucial for rational planning, management, and improving human well-being. Combining bagplots with correlation coefficients can not only determine the overall positive or negative correlation between two services but also visually express their spatial interactions, enabling the partitioning of trade-off/synergy zones and identification of dominant services across regions. The Taihang Mountains, as an important water conservation and soil retention functional area, serve as a critical ecological barrier and "water tower" for the Beijing-Tianjin-Hebei metropolitan region and the North China Plain. It undertakes significant ecological tasks such as climate regulation, water conservation, sediment retention, and biodiversity conservation. This study aims to explore the trade-offs and synergies among ecosystem services in the Taihang Mountains and, based on these findings, delineate ecological service zones to support ecological ecological conservation and high-quality development in the Taihang Mountains and the North China Plain. The study employed methods such as yield spatialization, the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model, and ArcGIS kernel density analysis to assess the provisioning services (food supply), regulating services (water yield and carbon density), supporting services (soil retention and habitat quality), and cultural services (leisure and recreation) of the Taihang Mountain ecosystem. By combining linear Pearson correlation coefficients with nonlinear bagplots, the study conducted an in-depth analysis of the interrelationships among these services. Furthermore, based on the bagplot results, the study identified the geographical patterns and dominant service distributions of ecosystem service trade-offs and synergies. The results indicate that: (1) There are trade-offs between food supply services and both regulating and supporting services, while most regulating and supporting services exhibit synergistic relationships with each other. Leisure and recreation services, on the other hand, show neither trade-offs nor synergies with other services, representing a compatible state; (2) The spatial distribution of trade-offs and synergies among ecosystem services is uneven, with the area of each zone closely related to the strength of correlation (absolute value of correlation coefficient); (3) The ratio of areas with strong synergy, strong trade-offs, and balanced synergy/trade-offs among multiple services is approximately 4:3:2. Regions where provisioning services dominate are mainly located in the plain areas and intermountain basins at the edges of the study area. Areas dominated by leisure and recreation services are mostly found in the shallow mountainous zones transitioning from eastern hills to plains. Other regions with higher altitudes, slopes, and vegetation cover are primarily dominated by regulating and supporting services. Identifying synergistic zones and dominant ecosystem services based on bagplots has important practical significance for optimizing the layout of ecological protection red lines, supplementing protection areas, and implementing regulations on the use of ecological spaces.