Help Zygarde EX vs Bursting Balloon

[Calcab]

Hey, something happened last league cup.
A player attacked with Zygarde's attack which heal damage a Pokémon with a bursting balloon attached.
Would the damage from bursting balloon trigger first (which would knockout zygarde in this case) or the Zygarde's heal trigger first (which would keep Zygarde alive)?
I read somewhere a similar example with Gengar's ability Vs Miltank's ability. If a player attach an energy, the player in question shall choose if he heals the damage from Miltank's ability or put the damage counters from Gengar's ability, but I'm not quite sure if the same rule applies in this case.
Thanks in advance.

 

[Professor_jplap]

Yes, you were right ; whichever you effect choose applies first

 

[sandsmash23]

The effects of attacks occur before damage calculation, so Zygarde-EX would heal first. A similar interaction was well-known between Shaymin-EX and Bursting Balloon, where if you Sky Return into what would be a knockout with a damaged Shaymin-EX, it will return to your hand without being knocked out. This was important in the Trevenant matchup, because two Shaymin-EX could just loop themselves until the player had a better opportunity to set up.