Weather Ball is supposed to be activated through the use of Normalium Z, but if the weather changes, that means the type for Weather Ball also changes to Water, Fire, Rock, or Ice, thus making it impossible to use with Normalium Z since it only allows for Normal type moves to work.

If a pokemon using Weather Ball with Normalium Z in no weather uses it, it is calculated solely as Breakneck Blitz with the base 50 power.

In the games, Weather Ball with Normalium Z is done by
In Weather: Double Base Power to 100, Change move to the weather (Sun - Fire, Rain - Water, Hail - Ice, Sandstorm - Rock), and then the additional Z-Power boost to the base power. The move is still Breakneck Blitz, but the type changes (so fire Breakneck Blitz)
Out of Weather: Base Power stays at 50, Z-Power Boost

Hey there Ale, thanks for the ticket! I can confirm that elementally-aspected Breakneck Blitz is not correctly applying the power boost from the Normalium Z crystal!

To test:
1) Give yourself a pokemon that knows moves such as Weather Ball, plus Sunny Day, Rain Dance, Hail, and/or Sandstorm. I used a Combusken. Also give it a Normalium Z, and yourself a /megaring - make sure to equip it.
2) I engaged a smiliarly-leveled Bulbasaur - I first tested regular Weather ball damage, which amounted to taking off about 17% of Bulba's hp.
3) /pokeheal, then engaged again, using Z-move Weather Ball - Breakneck Blitz (normal) does about 50% of bulba's hp.
4) /pokeheal, the engaged again, first using Sunny Day to change the battle-weather to sunny (fire), then using breakneck blitz, which turns to Inferno Overdrive....which only does about 17%, despite being super effective and should be powered by the Normalium Z.
5) /pokeheal, then engaged again, first using Hail to change the battle-weather to hail (ice), then using breakneck blitz which turns into Subzero Slammer, and which also only does about 17% despite being super effective.

As such, I will pass this on to the internal tracker! Thanks again!
Katzyn