They're very close in pronunciation, as both have an unstressed first syllable which is weakened. There is a slight difference, though. Most native speakers would pronounce 'precede' as 'priseed' and pronounce 'proceed' as 'pruhseed'. When you pronounce these words, remember to stress the second syllable.

to proceed means to go on, continue or start. for Example : Let's proceed to the next topic. precede besically means to come before some thing else for example : Strong winds preceded the heavy rain.