This is done on the Terrace Village level in Beast Makers world.
You want to progress to the end of the level, but instead of jumping to the platform that takes you back to the main world you glide to the one on the right.
Then jump up the 3 black/green boxes to the roof of the building, on the north facing side, you want to stand on the black/green ledge facing the bridge you crossed earlier then glide down to the top of the building to the left of the bridge.
From there glide across to the next building, this one connects to two other buildings that have golden platforms, each of these platforms will have a firework, blast both with fire and jump down to the ground towards the tunnel and youll see the 3rd rocket between the building you jumped off and the tunnel.
The rockets break open the un-smashable chests as well to the north of the bridge