If your engine is really the DLE35, the spark plug cap is 120 degrees angled , and it's a little bit difficult to remove than the standard 90 degrees CM6 plug cap. Last DLE ignitions with CM6 (120 or 90 degrees) have a weak circ-clip on the cap, and are easier to remove.
On this plug-cap , i pull hard while twist quikly at the same time, and that's the tip :twist and pull.
Best regards