Cairo is 5 hours behind Beijing
Best overlap: 1:00 PM to 6:00 PM in Beijing is 8:00 AM to 1:00 PM in Cairo.
1:00 PM to 6:00 PM in Beijing is when Cairo is also working, at 8:00 AM to 1:00 PM their time. Roughly 5 hours of common time means scheduling is manageable; just avoid the very edges of the window. The window above shifts seasonally: Cairo keeps daylight saving while Beijing ignores it.