When analyzing Zwifts metrics for tracking progress, what value can be placed on comparing functional threshold power (FTP) as a standalone metric versus incorporating it into a more comprehensive approach, such as the Performance Management Chart (PMC) which also considers chronic training load (CTL), acute training load (ATL), and training stress balance (TSB), and how do you account for the possibility that focusing solely on FTP may lead to an inaccurate assessment of overall fitness level, particularly for riders who are returning to consistent training after a prolonged period of inactivity, and are there any Zwift metrics that can better capture the nuances of a riders physiological adaptations during this transitional phase, such as changes in anaerobic capacity, aerobic capacity, or neuromuscular power output, and how can riders effectively integrate these metrics into their training to optimize progress and minimize the risk of overtraining or injury, especially in hilly riding environments where the demands on the rider are more varied and intense.