Hello Javelin,
While the APU is operating, the eductor, by using the kinetic energy of the exhaust gas stream, creates a negative pressure in the APU compartment. The two additional openings you see below the APU exhaust, on the aft tail cone, are cooling air inlet vents. Air is drawn into the APU compartment through these vents. The cooling air then flows through the oil cooler and ultimately is drawn into the APU exhaust stream by the eductor. The eyelid shields on the cooling air inlet vents are to prevent recirculation of the exhaust gases.
Best regards,
The Kid