They both have same stats as the regular formes, but their ability makes it so they go into a zombie mode. Which, for parasect, has these stats:
HP: 60 (Becomes half when it resuscitates)
Attack: 130
Defense: 40
Sp. Attack: 50
Sp. Def: 40
Speed: 105
A-Paras becomes A-Parasect when the item Xen Waste is used on them.