No, you cannot customize the Executive report. There is an option to rearrange the sections but you cannot remove or edit them from the report. The only option is to drag and drop (rearrange) the sections in the Executive Report.
Follow these steps to rearrange the section:
Navigate to Partner Center > Administration tab > Customize
Click on Business App Settings > Edit Default Executive Report Template
Click on the two horizontal lines next to the section and drag up or down