The most effective tactic was starting with identity-only enforcement before network segmentation. At Advanced Professional Accounting Services, we first rolled out ZTNA in monitor mode, validating identity, device posture, and access patterns without blocking traffic. The concrete checkpoint that made the biggest difference was a legacy app compatibility review tied to real user sessions. We mapped which apps relied on hardcoded IPs or long-lived connections and added app-specific connectors before enforcing policy. That step prevented breakage and built trust with users. Once visibility was proven, we phased into least-privilege rules with minimal friction.