Complex sentence: Produced during 1955, the film went into theaters in the early summer of 1956, just ahead of the TV syndication by Universal Pictures of its two decades of "monster movies" through Screen Gems, under the package title of Shock Theater.
Split into simpler sentences: Produced during 1955, the film was released to theaters in the early summer of 1956. This was just ahead of the TV syndication, through Screen Gems, of two decades of Universal monster movies, under the package title Shock Theater.