Can't unscrew the last two screws
I tried to open my MacBook Pro 2012 (RAM change and replacement of the HDD by a SSD) using the iFixit Tools (Philipps #0), but I've got 2 screws that I can't unscrew (sorry for my english, I'm french). I tried slowly, but the screw didn't turn. After 3 or 4 tries, the "cross shape" is damaged, so I don't know how to get rid of those two screws... Anyone has a solution ?
Here is a picture of the screw (the other look the same) :