The rapid digitization of healthcare delivery organizations has precipitated a complex security landscape characterized by the proliferation of Internet of Medical Things (IoMT) devices and an increasing reliance on legacy infrastructure. This research provides a deep theoretical and empirical evaluation of the transition from traditional perimeter-based security to Zero Trust Architecture (ZTA) within the clinical environment. By synthesizing contemporary frameworks, including the Zero Trust Maturity Model and the Zero Trust eXtended (ZTX) ecosystem, this study examines the inherent vulnerabilities of trust as a structural flaw in network design. Central to this investigation is the challenge of bridging ZTA principles with legacy medical devices, specifically focusing on the adoption of modern operating systems like Windows 11 in hospital clinical workstations. The study employs a multivocal literature review and qualitative analysis to identify critical research gaps, such as the perception layer security in IoMT and the scalability of federated learning and blockchain in IoT-enabled healthcare. Results indicate that while ZTA significantly reduces the lateral movement of threats, the modernization of legacy systems remains a primary bottleneck due to technical debt and clinical continuity requirements. The article concludes by proposing a comprehensive roadmap for healthcare organizations to modernize their cybersecurity posture while maintaining operational efficacy, emphasizing that the elimination of implicit trust is the only viable path for securing the future of urban and regional health.