That is not a CR 2 opponent, IMHO, regardless of conjure animals. If you only look at it's AC, HP and melee attack... it's tougher than a CR 2 ogre. +1 AC, +1 average damage, and +32 (!!) HP.
Plus it has disease, immunities, zombie toughness, pack tactics, and a 5th level caster spell-list. So...