Zodiark isn't hard per se, only in the part where he puts the paling and magick shield on. The main problem with him, is that he tends to spam Darkja at will, which has a 50% chance of instant death or 25% if you equipped Demon Shields on your chars, and sometimes he would use it 5 times in a row.
With Paling and Magick Shield he was invulnerable to your attacks most of the time, except for a small window of opportunity where the magick shield went down for a few seconds, which you could bombard him with Shock or use a Quickening in which if you were lucky enough, you would kill him in one go. While this window of opportunity didn't appear, you would have to stand up to him casting Shock, Scourge (not Purge, sorry for before), Scathe and Darkja.

So you see, it wasn't hard per se, it was more a matter of sheer luck.

Edit: Wrong thread. :/

I'm surprised this hasn't been said yet:

Combine "Knights of the Round" with "HP Steal" materia.
Combine a max level "Counter" materia with "Mime" materia.

At the start of either Ultimate Weapon battle, using the character equipped with the materia combo listed above, cast Knights of the Round. Now, do nothing.

Every time your character with the materia combos above is attacked, he or she will counter with Knights of the Round at no MP cost, leeching back 9999 health. You can literally walk away from the battle and come back a few minutes later to the victory screen.

I'm guessing by HP Steal you mean HP Absorb?

Yeah, thanks for correcting me.

Can you tell it's been a while since I played?

Well, the game is 12 years old.

Well, I did it.

Using Counter linked with Mime and 45 minutes worth of Hades/Knights of the Round attacks, I beat Ruby Emerald.

I fu**in did it, I FINALLY did it.

Emerald is next.

Congrats, if you beat Ruby, then Emerald is a joke comparatively speaking.

Also for the FF veterans, how often did Ruby pull his arms back out after you enter the game with two dead friends. I always had Phoenix/FA on and always had 3 guys fighting Ruby by the end. Of all the times I beat Ruby he pulled his claws back out once. Maybe I am remembering it wrong, but I thought once Ruby put his arms in at the start he rarely pulled them back out. (US version)

I'm glad you pulled it off! Congratulations.

The good news is that Emerald is a snap once you beat Ruby. Good luck.

Using Hades on Ruby paralyzes/stops him for a few turns so you can hit him with KotR few times before he can move again. Repeat.