Questions About Zirconaide & Jade WEAPON

[Gym Leader Devil]

How is it possible to completely kill a summon anyway? I thought it had been confirmed that they were just energy constructs built of Mako from the memories of legendary beings accessed through materia? And that, like a fire spell for instance, you could summon them over and over no matter what happened during the prior summoning (unless it burns all life on the Planet to ash of course). After all, Zack beat the shit out of both Ifrit and the original Bahamut in CC, but they're still available to summon in the OG. Or am I looking at it wrong?

 

[The Twilight Mexican]

Shears shattered his materia after he had been summoned, so when the Turks killed it, it was dead permanently.

 

[Gym Leader Devil]

Dead permanently? Or just till the Planet spits out another one? *cue ominous music and roll credits with a big goofy sign that says The End transforming into a ?*