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!
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!