Trouble disassembling PS3 Dualshock 3 controller

The left analog stick on  my CECHZC2E A Dualshock 3 PS3 controller broke and I'm trying to replace it. I've disassembled controllers of other models before and all was going well at first. Unfortunately I encountered a problem. There seems to be 2 plastic slots on each side of both rumble motors. No matter what I do I can't slide the rest of the plastic part out which prevents me from getting at the analog sticks. I'll try attach some pictures to help you identify my problem. Hopefully it can be solved