Zoox, Amazon’s self-driving unit, is bringing its autonomous vehicles to more cities. The self-driving technology company announced Wednesday plans to begin testing in Austin and Miami this summer. The two cities mark Zoox’s fourth and fifth test cities, following Las Vegas, San Francisco and Seattle. The news comes as federal regulators increase their scrutiny of self-driving car companies like Waymo and Zoox, both of which are under investigation over safety issues. Earlier this week, the Nati...