Identifying quick wins for implementation first is the best approach to gain support for the process, as it can demonstrate the value and feasibility of the project, and motivate the stakeholders to overcome the resistance and embrace the change12. Quick wins are those actions that can be implemented rapidly and easily, and that can produce visible and measurable results3.
References7 Phases in COBIT Implementation | COBIT Certification - SimplilearnImplementing the NIST Cybersecurity Framework Using COBIT 2019, page 17.What is a Quick Win? - Definition from Techopedia

According to the TM Forum's Business Process Framework (eTOM), the business/process level is responsible for defining the business strategy, objectives, and requirements, as well as monitoring and controlling the performance and quality of the processes1. The implementation/operations level is responsible for designing, developing, and executing the processes that deliver and support the services1. When coordinating framework implementation, these two levels collaborate to assess changes in current and future risks, such as market trends, customer expectations, regulatory compliance, security threats, and operational issues2. This helps them to align the processes with the business goals and outcomes, and to identify and mitigate any potential gaps or challenges3.
References: 1: Process Framework (eTOM) - TM Forum 2: Implement Dynamics 365 with a process-focused approach 3: Operations Management Implementation - Smarter Solutions, Inc.

Identifying external compliance requirements is most likely to occur during COBIT Implementation Phase 2:
Where Are We Now?, because this phase involves assessing the current state of the enterprise's governance and management system, as well as its strengths, weaknesses, opportunities, and threats12. This phase also includes identifying the relevant stakeholders, drivers, and scope of the implementation program . Therefore, this phase requires a thorough understanding of the external laws, regulations, and contractual obligations that apply to the enterprise and its I&T activities.
References: 1: COBIT 2019 Implementation Guide 2: COBIT 2019 Implementation - ISACA : Connecting COBIT 2019 to the NIST Cybersecurity Framework - ISACA : 7 Phases of COBIT Implementation:
Explained - The Knowledge Academy : Compliance with External Requirements - Morland-Austin

The objective of COBIT Implementation Phase 3 is to set an improvement target and identify gaps and potential solutions using COBIT's guidance. This involves creating a detailed business case and a high-level program plan for the implementation.
ReferencesCOBIT 2019 Design and Implementation COBIT Implementation, page 31.7 Phases in COBIT Implementation | COBIT Certification - Simplilearn

According to the NIST Cybersecurity Framework, an organization should review cyber threat information from internal and external sources to gain a better understanding of the likelihood and impact of cybersecurity events. This information can help the organization to identify potential threats, vulnerabilities, and consequences, and to assess the current and target profiles of its cybersecurity posture12.
ReferencesIdentifying and Estimating Cybersecurity Risk for Enterprise Risk Management, page 19.COBIT VS NIST : A Comprehensive Analysis - ITSM Docs