Pasar de panzazo, “to pass with a belly flop,” means to pass an exam or a test with the minimum grade. The Diccionario del español de México records it as popular speech.
In 2012, the phrase gave its title to De panzazo, a documentary on the state of education in Mexico by the filmmaker Juan Carlos Rulfo and the journalist Carlos Loret de Mola. Spanish Wikipedia says that it broke a box office record that year. (Video in Spanish.)