If the Guyver gives the user 100 times more power than the original form, then the Gigantic would boost the power of a Guyver Unit 100 times over! Making the Guyver unit as powerful or even MORE powerful then a Zoalord.

Uptil Chapter 140, 1 Zoalord has already been killed and one seriously injured in one to one combat.

The Gigantic is not a creation of the Creators, but an image from Sho's mind, an image that he wanted to create to win over the Zoalords and save his friends. The Control Metal of the Creator's ship knew that and fused with Sho just before he was destroyed by Archanfel and granted him his wish. For all we know the Control Metal on the Gigantic could be the actual Control Metal of the Creator's Ship.

The Head of the Gigantic looks strangely BIG though... ...