For a limited time, Zarude will appear in Pokémon Go if you are able to receive the exclusive Special Research. The Special Research will be available during the Pokémon the movie: Secrets of the Jungle event, which starts October 1 and runs until October 11. All you have to do is make sure you jump into Pokémon Go to receive the mission, and then you can complete it at any time, even after the event has concluded. Zarude will be a guaranteed reward for this mission, and when you meet him, will you be able to catch a sparkling Zarude?
Unfortunately, the brilliant version for Zarude will not be available for this mission. Since this event is Zarude's debut on Pokémon Go, a bright version will not appear. Developer Niantic does this for every new version of Pokémon for mobile play, especially when it comes to Mythical Pokémon.
For many Mythical Pokémon that appear in Pokémon Go, an exclusive event focused on the glossy version and most players have an equal opportunity to catch it. Typically, the chances of catching a bright version of any Pokémon are pretty low. But for Mythical Pokémon, most have a good chance of being brilliant when the event unfolds. However, Meltan has some of the more difficult chances of being a brilliant version, mainly due to the frequency with which it appears in Pokémon Go.
We can expect the brilliant version of Zarude to be released when he appears next time, after the Pokémon the movie: Secrets of the Jungle the event has concluded and Niantic presents another event.