Damn. Not even a sucky translation can stop that scene from being epicness personified. Except...the transformation. I dunno why, but the EG form doesn't have quite the same "OH SH**" quotient as watching evil ghost Zeromus turn into freakin' cosmic horror Zeromus just as the final boss theme picks up.
The only sane reasoning for the image change is that FF4 came first and someone thought it was a good idea to make the game a bit more district... besides changing his battle script.
And yeah, that all-party Doom number...that's cheapness personified, and this is coming from the man who magically goes back to full HP in the middle of the fight without any visual cue whatsoever.
Why not? Advancing the climax of his death is better than his Meteor attack that does putrid damage, if not get automatically evaded due to high magic evade (2x multiplier with 30+% magic evade is more than enough apparently). The full HP issue is a clever way of increasing the max HP of the beast (this boss has to be facing the 16-bit variable HP limit).. yet in can be avoided altogether if you expose one particular bug.
On that subject, just what is that Hug (Embrace?) attack supposed to do again? Something tells me it's not meant to be Zeromus' idea of playing fair by restoring Rosa's HP in the middle of the battle...
Hug/Embrace is supposed to inflict Stone status and full healing to the target. Regardless of Stone status being inflicted, the healing is dealt (like many HP+status inflicting attacks). I've already gotten around to fully documenting (just writing the behavior down, not that most romhackers don't already know) all the spells for the game. The attack itself is non-threatening when everyone has protection against Stone status.. which is generally everyone that has a Ribbon (you get two of them) or an Aegis Shield.
The Call Books is the FF4A's terminology of the regular Grimoires. A random summon (other than Asura) is selected from all the standard summons (minus the special monster-item dropped summons) with a spell multiplier of 8.
The item drops are radically different in FF4ET. The Call Books tend to drop relatively frequently (Imps/Goblins are the best bet), which already existed in the original game as rare drops. These items are not really that useful once you are able to face Asura or Leviathan, but allow you to breeze through the original game quickly if you wanted to...