Both Z-Moves look similar, teleporting the target Pokemon to another dimension to receive a particularly brutal attack.
Pokemon Ultra Sun and Ultra Moon has a new trailer out that reveals some exciting and explosive new features. Hopefully, it won't get in the way of Pokemon Ultra Sun and Ultra Moon telling a coherent, engaging story that actually has a satisfying ending.
When Dusk Mane Necrozma is holding Solganium Z, it unlocks the Z-Move Searing Sunraze Smash. Both moves cause an opponent to be sucked into Ultra Space, where they are then hit by Solgaleo or Lunala's signature move.
It's also worth pointing out that Necrozma, whether fused to Solgaleo/Lunala or not, will have a new move that is exclusive to it. Photon Geyser is a new Psychic-Type move that can deal substantial damage to an enemy and dictates how much by determining which of the Attack or Special Attack stats are higher (per PokemonDB).
The interesting point for the hardcore fans, though, is the set of changes that are coming to the Rotom Dex - Sun and Moon's version of the traditional Pokédex. As players befriend the floating PokeDex/Pokemon hybrid, RotomDex will unlock new abilities to make the player's life a lot easier. When players bond with Rotom they can use a number of his features so that they can hatch Poke' Eggs faster and run into stronger Pokemon in the wild. In addition to the ability to use Z-Moves a couple of times in a battle, Rotom will also give stat, experience, and money boosts as well as faster egg hatching in a fashion similar to the O-Powers of the sixth generation Pokémon titles. The trailer strongly hints that this ability is only available for the in-game storyline and not in any sort of competitive play.
Pokémon Ultra Sun & Ultra Moon launch on November 17 for Nintendo 3DS systems.