How to define if brake pads suitble for carbon clinchers
Yes, you need special pads. Every manufacturer of carbon rims has their own recommendations for what pad to use, which you should follow. Zipp makes their own pads.

Normal brake pads are harder, and can wear away the carbon rim surface. This is very bad, of course. Brake pads for carbon rims are softer and wear down more quickly so that they preserve the rim.