Absolute Zero Question

In a hero mirror match i have a ab zero on the field. My opponent has no monsters and plays mind control and then miracle fusion using my ab zero as a fusion material. Does the new fusion that he summons with miracle fusion get destroyed by zeros eff or does zeros eff activate and afterwards the fusion monster is summoned?

Yes

The controller of zero owner is the one who get effect.

I mean does my opponents fusion monsters die from zeros eff or is it summoned after zeros eff is applied meaning it doesnt die.

Zero effect is mandatory,
you opp monster should be destroyed with Zero effect after he summon his fusion monster

Correct, the new fusion will be destroyed. If he makes the Shining he can +1. Else its his loss.