Complex sentence: Zachariah Eastin was seven years old when he moved with his father from Virginia to Bourbon County, Kentucky, at the time Boonesborough, and Bryant's Station, were established by the leaders in the Euro-American incursion into Shawnee lands.
Split into simpler sentences: Zachariah Eastin was seven years old when his family moved from Virginia to Bourbon County, Kentucky. This was during the time Boonesborough, and Bryant's Station, were established by the leaders in the Euro-American incursion into Shawnee lands.