Hi! This pack requires OptiFine to work and changes the texture of elytra to match the armor.
If you want new texture you should just rename Elytra to:
Netherite Elytra
Diamond Elytra
Gold Elytra
Iron Elytra
Chainmail Elytra
Leather Elytra
This pack also has two versions: thin and thick. Check out images to see difference!
Hope you like it!
_daggsy_