The rapid migration to multi-tenant cloud environments has amplified the complexity and attack surface of enterprise infrastructures. Traditional perimeter-based security models are increasingly ineffective against advanced threats, lateral movement, and identity compromise. In response, the Zero Trust Architecture (ZTA) has emerged as a robust security framework grounded in the principle of “never trust, always verify.” However, operationalizing Zero Trust in cloud-native environments characterized by dynamic workloads, containerization, and cross-tenant resource sharing requires a fine-grained, adaptive enforcement strategy. This paper presents a comprehensive Zero Trust enforcement model that integrates microsegmentation, identity-aware proxies, and continuous adaptive risk assessment (CARA) to secure user, workload, and application interactions within multi-tenant cloud ecosystems. Microsegmentation enforces least-privilege access through granular, workload-level network policy controls, isolating environments to limit breach propagation. Identity-aware proxies authenticate and authorize every request based on real-time context, leveraging attributes such as device posture, user role, geolocation, and workload metadata. In parallel, CARA dynamically scores risk based on behavioral analytics, historical access patterns, and threat intelligence feeds, enabling context-aware access decisions and policy adjustments in real time. This tripartite approach ensures that access to cloud resources is continuously evaluated, even after initial authentication. The paper evaluates implementation strategies across AWS, Azure, and Kubernetes-based architectures, addressing challenges such as policy drift, latency trade-offs, and cross-tenant policy orchestration. A reference model is proposed for deploying Zero Trust controls in highly elastic, distributed environments. By combining these technologies into an integrated defense framework, this work advances the practical deployment of Zero Trust principles, enabling resilient, scalable, and adaptive security in the modern cloud.