Using Google Drawings, Excalidraw, or any exercise tool of your choice, diagram out the timeline of work from the formatting exercise. Then put the diagram in the doc that you previously did to really bring home your point to show the leadership team what the timeline is.
To recap, the team is going to take 2 weeks in August to design. No other work can start until the designs are finished. Then, once the designs are done, both the UX research team can start research which will take two weeks, and the developers can start their coding implementation which will take four weeks.
Chart out a visualization that emphasizes the overlapping nature of the work.