Geologically, the range is rooted in the formation of a subcontinent from a region of Gondwana that drifted away from East Africa about 160 million years ago, around the Middle Jurassic period. The Indian subcontinent, Australia and islands of Indian Ocean rifted further, drifting northeastwards, with the Indian subcontinent colliding with the Eurasian plate nearly 55 million years ago, towards the end of Palaeocene. This collision created the Himalayas, including the Hindu Kush.

What's the best answer to this question: are the hindu kush mountains part of the himalayas?
yes