Bon finalement j'ai trouvée la réponse par moi-même, donc merci... moi.
Where is this jumping puzzle?
It is inside the Mad King's Labyrinth that you can access from Queensdale, Kessix Hills, or Gendarran Fields. Go into any of those zones, if you see pumpkins all over the map, head to one of those and enter the door. Once inside the Mad King's Labyrinth, talk to the NPC and ask to go to the Mad King's Clock Tower.