The printed circuit heat exchanger (PCHE) is recognized for its high heat transfer efficiency and pressure resistance. Among different channel configurations, including airfoil-fin, straight, zigzag, and S-shaped channels, the zigzag channels demonstrate the best thermal performance. For the design of zigzag PCHEs, accurate correlations for the Nusselt number (Nu) and friction factor (f) are essential. However, the existing correlations in the literature for Nu and f differ significantly in form even under similar conditions and have limited applicability. Thus, it is necessary to evaluate correlations that apply over broader ranges or to develop accurate correlations if necessary. This study initially evaluates the accuracy of existing correlations using approximately 2150 data points, with Reynolds numbers spanning from 1.3 × 102 to 1.0 × 105 and Prandtl numbers ranging from 0.7 to 10.0. Our findings reveal that most correlations have errors up to 35%, with some exceeding 55%. To enhance prediction accuracy and extend the applicability, new correlations are developed by considering various structural parameters of the zigzag channels, such as the bending angle and longitudinal pitch. These newly developed correlations significantly reduce the error, with the Nu and f error ranges decreasing to below 11.29% and 20.42%, respectively. These new correlations have a wide range of operating conditions and are particularly suitable for high-temperature applications, i.e., advanced nuclear and concentrated solar energy systems.