It's easier to do them separately.
I think the fact Floor 10 has Ultima Demons and Summoners with Zodiark is because they made sure these aren't missable skills anymore. So I THINK that every Summoner you run into on Floor 10 (in subsequent random battles) will have Zodiark even if you didn't get it the first time around, and you don't have to worry about it on your first clear if you just want to beat Serpentarius and come back.
Learning Zodiark is easiest if you have the Summoner trying to learn it go in with 97 Brave and Manashield so that they can tank the damage for sure and live. The biggest issue is making sure that other enemy units don't blitz that unit's mana before the cast goes off. You can't use Atheist to survive the cast since the Zodiark actually needs to do damage to the target for the target to learn it (damage to Manashield counts).
You can also nuke your learner's Faith to lower hte damage. A lot of people have been saying that it's optimal to have units with super low Faith on Tactician mode since enemy magic is broken and magic is inferior as a damage mechanism in the game anyway. But I personally don't nuke my units' faith scores because it screws up Raise casts (and I prefer Arithmaticks as a support skill to Items), and what's the point of learning the skill if you have nerfed it to uselessness?
Also technically you can just skip getting the Chaos Blade and Chirijiriden on Floor 10 if you just catch them in Floor 9. The fact everyone can wear Perfume now means you can give everyone a Chaos Blade (versus OG/WotL where you just give Chaos Blade to Agrias with the perfume and everyone else wears Excalibur for the Haste)
The Rubber Suits are worth farming too btw. They have more HP than Crystal Mail and Reflect Mail and give immunity to Lightning (you can spam Calculator Thundaga as an alternate to spamming Calculator Holy with Chameleon Robes).
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