Z-Power training could roughly be divided into five stages.
First Stage.
A Pokémon carried a Z-Crystal, while the Trainer wore a Z-Ring made from a Shining Stone, and together they used a Z-Move.
The representative combination was Fang Yuan and Venusaur.
Second Stage.
The Pokémon had relatively proficient control over Natural Energy and light energy. Even without carrying a Z-Crystal, it could still use Z-Moves with the Trainer's help.
The representative combination was Fang Yuan and Eevee.
Without carrying a Z-Crystal, Eevee could use Fire-type and Psychic-Type Z-Moves with Fang Yuan and the Z-Ring's assistance.
Third Stage.
The Pokémon had an exceptional mastery of Natural Energy and light energy. Even without a Trainer, Shining Stone, or Z-Crystal, it could independently use Z-Moves.
The representative Pokémon were Ho-Oh's Messenger Marshadow and Dual Wielding Style Swordsman Groudon.
Of course, independently using Z-Moves required them to be of an attribute the Pokémon was skilled in.
For example, Groudon could use Fire-type Z-Moves without any external aid, but if it wanted to use Flying-type Z-Moves, it would still need a Z-Crystal.
The Fourth Stage.
Building upon the first three stages, Pokémon could independently condense Z-Crystals of every type and use autonomous Z-Moves of any type. Mewtwo was at this stage.
As for the Fifth Stage.
That was the level of the Tapu Family. They could help other Pokémon cultivate exclusive Z-Moves and condense special exclusive Z-Crystals.
Anything beyond that could wait until Fang Yuan managed to network with the Shining God.
Z-Power training primarily depended on a Pokémon's talent for controlling "Natural Energy" and "light energy."
Within Fang Yuan's Team, only Eevee and Venusaur had the best talent in this regard.
Therefore, Fang Yuan hoped that both of them could reach the Third Stage in their use of Z-Power.
With Groudon and Mewtwo teaching