I thought you were referring to the one in Mt. Gagazet. The Species Creation one is much harder to beat.

First off, cast reflect on one of your characters (only one and rely on X-Potions to heal that character. Use shell/Lunar Curtains if you have them (useable with the USE command, not Item). After that have a character doublecast Flare off the Reflected Character, or use Ultima. After that, copycat if you have it.

I suggest completing the entrie Sphere Grid if you don't want to have to put up with the annoying concept of "dying". Otherwise, follow the instructions.

The Jumbo Flan is more annyoing than most of the Original Creations.
PM or post if you need help. Or AIM. That works too.