First, we present the performance evaluation of the IP-CVS-EOM-CC method through a comparative analysis of calculated core-ionization with corresponding experimental values for core65 dataset. We also investigated the effects of the frozen core approximation and scalar relativistic effects on determining core-ionization energy. Subsequently, we illustrate the convergence of the core-ionization energy relative to the embedding space. Utilizing the optimal embedding space information, we assess the performance and scaling advantages of the DMET-based method for the amino acids molecular set. Finally, we report the coreionization of uracil-hexamer, azafullerene, and chlorophyll a using the DMET-based method, which would otherwise be intractable with current unembedded EOM-CC methods.