While

Subordinating conjunction

  working

Verb

  with

Adposition

  Quechua

Adjective

  Indians

Proper noun

,  Elliot

Proper noun

  began

Verb

  preparing

Verb

  to

Particle

  reach

Verb

  the

Determiner

  Huaorani

Proper noun

.

While working with Quechua Indians, Elliot began preparing to reach the Huaorani.

While working with Quechua Indians, Elliot began preparing to reach the Huaorani.