Pokemon Box ruby and sapphire zigzagoon changing nature

[Superfighter26]

hello, im new here 
i tried to change the nature of the extremespeed zigzagoon but it always illegal.. i want to change the nature to adamant 
any solution?

263 - Ziggy - E954BC0593DC.pk3

[SkyLink98]

Reroll the PID after changing the nature.

[BlackShark]

PKHeX doesn't generate valid PIDs for Gen 3 & 4. You need to use external tools like Pokefinder as explained in the guide below.