Complex sentence: The first part of the crossover aired on "The Flash" on December 2, followed by part two on "Arrow" on December 3, both on The CW, and also aired in Canada on the same nights on CTV Television Network.
Split into simpler sentences: The first part of the crossover aired on "The Flash" on December 2, followed by part two on "Arrow" on December 3, both on The CW. The crossover also aired in Canada on the same nights on CTV Television Network.