Complex sentence: In September 1957, the model AZLP (P for "porte de malle", "boot lid"), appeared with a boot lid panel; previously the soft top had to be opened at the bottom to get to the boot.
Split into simpler sentences: In September 1957, the model AZLP (P for "porte de malle", "boot lid"), appeared with a boot lid panel. Now the soft top no longer had to be opened at the bottom to get to the boot.