Complex sentence: Once Edith orders Kevin the Minion to zap the riders, he pulls a lever transformed into minions or minionized by the minion gun and get pushed down a long tube to training by the girls.
Split into simpler sentences: Once Edith orders Kevin the Minion to zap the riders, he pulls a lever which activates the Minion Gun, transforming the riders into Minions. Next, the riders get pushed down a long tube to training by the girls.