Alright, I had checked as best I can and never saw this question answered. If I make an attack with Bossk equipped with prey on the week, if the target is of lower cost the attack gains pierce 1 and I spend a surge to pierce 2 as well, are the 2 and 1 added together to get 3 and then reduced or would zillo reduce them both first?

They add together for Pierce 3 then Zillo removes 2 of the pierce and there is an end result of pierce 1

If multiple Pierce abilities are used during an attack, their values are added together.

Zillo works on the one single total pierce value of the attack (it uses singular).

Edit: Ninja'ed.

Another question I have on Zillo Technique. I see that reducing the value of an attack by pierce 2 is a once/round effect as you have to exhaust the card. What about the second effect on spending command cards to increase block by 1. If Zillo technique is exhausted can I still trigger this effect?

Yes, the other ability that does not have exhaust as a cost is always available.

(But all abilities on a card that is depleted would no longer apply.)