"X-Head Cannon" + "Z-Metal Tank"This card can only be Special Summoned from your Extra Deck by removing from play the above cards on your side of the field. (You do not use "Polymerization"). This card cannot be Special Summoned from the Graveyard. Discard 1 card from your hand to destroy 1 face-down Spell or Trap Card on your opponent's side of the field.
No, Desert Twister is still much better. Desert Twister's summoning conditions are much easier to meet, since you don't need to run mediocre cards + have them be on the field, and XZ Cannon only destroys face down spells/traps, so you can't destroy TK, and other cards can still be chained easily.