Zane Under Cover capstone and shield interaction

So how does Zane’s capstone work with different type of shields?
ex:
-nova shield: does the nova goes off constantly or just when skill end? The latter would go directly against the tree.
-melee shield: probably double the bonus? but does it work for your friend? like when they’re near or inside the dome…
-shield with crouch shield: useless?
etc…