The Z Staff (also commonly spelled "Z-Staff") is a tall silver scepter with the letter Z on the top of it that is the iconic signature weapon of Lord Zedd and one of the many well-known objects in the Power Rangers universe. When combined with the Magic Wand wielded by Lord Zedd's former henchwoman-turned wife Rita Repulsa, the magic of both of these galactic villains' signature staffs amplifies and can do a variety of amazing, yet dangerous feats and in their quest to destroy the Power Rangers, such as transforming their monsters to an "economy size" as Rita would say.
The Z-Staff, though originally a transformed snake at the beginning of Mighty Morphin Power Rangers's Season 2 upon Lord Zedd's return to the Moon Palace, was one of the methods used by Lord Zedd for the creation and (more rarely) enlargement of his monsters, but he also showed that it a raw potential for sorcery, making it usable for general-purpose spellcasting. In different instances, Zedd used it to open dimensional gateways, create illusions, fire energy bolts and other magic feats unrelated to the creation and transformation of monsters.
It was also used at different times by Rita Repulsa, Goldar, and Rita's brother and Master Vile's son Rito Revolto, which proves that others besides Lord Zedd can use the staff even without his permission. Finally, it is worth noting that the Z-staff seems to allow the spellcaster to do magic from extreme range, since the MMPR villains regularly used it to cast spells from the Moon Palace on Planet Earth's moon with the utmost ease.
Though not exactly fragile, the White Ranger Tommy Oliver proved in his solo fight against Lord Zedd that it is perfectly possible for a slightly augmented human to break the staff.