Let my try explain to you, english isnt my first language BTW.

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I will use 2 pokemon that discard energy when attack:

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• **Blacephalon GX** *lost zone energies then do damage*, so for example: it had 3 energies on it, lost zoned 2 (2x50=100 due weakness 200) then damage Shuckel, but because it had just 1 energy in the "damage step" Shuckel became immune.
• **Turtonator GX** *do damage then discard the energies*, so for example, it does 320 damage (160x2 damage due weakenss) knocout Shuckel then it discard the energies

I hope its clear, Blacephalon GX need to have 5 energies in the entire process , the 2 energies that are lost zoned to knockout Shuckel and 3 energies in Blacephalon GX to bypass Shuckel's abilities.