Maybe I was lucky, but when I mixed Helephant and Stormzilla with 2 of my wizards, both of them got a Burnzilla. They are orange with stripes on their backs. I can't tell you any other stats right now, since I'm at work, and can't log in right now.
They both have a higher pedigree than Helephant and Stormzilla though. I'm not sure if they have an attack spell.
When you combine a helephant and a stormzilla, you have a chance of getting a maelstrom oni or a burninator. You also have a high chance of getting another one of the pet you hatched with, only with a different pedigree and different stats.
Most people just expect to get what they want, when they want it, and complain and rant when they dont.
If at first you dont succeed, try try again.
It took me multiple attempts to get an archfiend on test before I finally got one.
Also, both sides have a chance of getting a hybrid pet, and reguardless of what some may say, while all hybrids require certain pets to be made, none of the hybrids are school restricted (i.e. a burninator is not restricted to storm or fire, but require a helephant and stormzilla for a chance to be made.)