How would Papua New Guinea fare with a Shaka Zulu type Figure in the 1100s

The idea is for a Shaka Zulu type figure to conquer all of Papua New Guinea in 1100s and unite it. What would it mean for Papua and the rest of the Indonesian archipelago.
 
Is the terrain really that impossible?

All of the area conquered by Shaka Zulu spoke languages from the same dialect continuum. Meanwhile, people from two adjacent valleys in New Guinea speak languages as distantly related as English and Chinese. There are barely trade routes in most of the highlands, how could you have an empire?
 
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