Complex sentence: While the battles for Rethymno and Heraklion had been more successful, Maleme had been lost to the Germans, and the German control of the airstrip there, coupled with their total air superiority meant that the Luftwaffe could now land infantry and equipment by plane.
Split into simpler sentences: While the battles for Rethymno and Heraklion had been more successful, Maleme had been lost to the Germans. The German control of the airstrip there, coupled with their total air superiority, meant that the Luftwaffe could now land infantry and equipment by plane.