Unaffected by item negating effects (such as Embargo and Klutz). Item manipulating effects (such as Trick and Fling) cannot remove a Z-Crystal from a Pokémon.
In SM090, Gladion received a Lunalium Z from Lunala. Together with Ash and Nebby, Gladion and Lunala performed the Z-Move and provided enough light to help Necrozma restore its Ultra form.