all vĕdhams which are of four classifications —

 all vĕdhams which are in four categories —

rig, etc., the four vĕdhas, —

four types of vĕdhas, and —

 four vĕdhams —

vaidhikas who are experts in the 4 vĕdhams —

 with four vĕdhams —

 vĕdhams which are best among the pramāṇams [authentic texts] and are of four types —

 experts in four vĕdhams —