>>55661206Sycamore has a female ancestor with association to Team Flare.
Lysandre has a male ancestor with no association to Team Flare.
Sycamore's ancestor wants to catch/use OG Zygarde and possibly Xerneas.
Lysandre's ancestor wants to catch/use shiny Zygarde and possibly Yveltal.
In the end, both Zygardes merge together. That merged form can then Mega Evolve into a massive Eternatus-level threat.
That's my interpretation anyways.