Elytra not rendered on entities/mobs

Elytra is not rendered on entities (zombies, armor stands, ...)

/replaceitem entity @e[type=Zombie] slot.armor.chest minecraft:elytra

This report is definitely valid.
For example Zombies with CanPickUpLoot:1b will equip the elytra:

/summon Zombie ~ ~ ~ {CanPickUpLoot:1b,Health:0.1f}