The Zora Armor Set returns to Tears of the Kingdom after Breath of the Wild. It remains one of the sets with the most useful abilities in the game: Swimming up waterfalls. Although you only need the Zora Armor to get access to that ability, completing the sets gives Link the Swim Speed Up buff that allows him to cross bodies of water like a fish.
You will acquire the Zora Armor as part of the Sidon of Zora questline, but to acquire the Zora Greaves, you will need to complete A Token Of Friendship Quest given to you after the Water Temple has been cleared. Talk to Yona, the now queen of the Zora, to initiate the quest.
Starting The Quest
To start this quest, you will first have to complete the Zora portion of the Regional Phenomena questline. After completing Sidon of Zora, you will see Yona, Sidon's wife-to-be standing right in front of the throne room, overlooking Zora's domain from a small balcony.
Talk to Yona to begin the quest. She will say that she wants to give Link a special gift in the form of a set of Greaves that has been passed down in Zora's history. The Greaves in question are lost, though, and no one knows where they are anymore except for the fact that they might be somewhere in the Ancient Zora Waterworks.
Finding Zora Greaves
Open the map to find the Zora Ancient Waterworks. The closest teleport point near their location is the Ihen-a Shrine. Teleport to the shrine and climb the waterway all the way up to Mipha's statue. Jump off from the top to find the whirlpool at the center of the lake. You will have to dive into the whirlpool to reach Ancient Zora Waterworks.
Climb out of the water and paraglide over the pool with the wooden planks. You'll see a staircase going downward. At the end of the stairway, you'll see Gruve overlooking the waterworks.
In front of Gruve, the stairway opens up to a large ruin with lots of debris and broken rocks littering the ground. In the middle of the ruin is a tall tower that you had to reach the top of when doing Sidon's quest. At the base of this tower, on the side opposite to where Gruve is standing, is a hole in the ground.
Dive into this hole to reach the bottom. There, you'll see a large cavern with three waterfalls, as shown in the picture.
Head towards the waterfall in the back. Take care to avoid the Stone Talus that's hiding in the middle of this cavern. Once you reach the waterfall, you'll notice there is a room hidden behind the water. Enter this room, and you'll see a chest. Open the chest to find Zora Greaves and complete A Token Of Friendship side quest.