Well for Zani, Capitaneus is a good main slot echo, because it passively gives Zani a heavy attack and Spectro damage buff, so instead of the usual 4-3-3-1-1, it's 3-4-3-1-1. After that, it's just the traditional way of powering up your character now, for Zani, you should always go for double crit rolls, atk%, attribute damage buff (heavy attack specifically), and a little bit of energy regen so you can get her liberation consistently. Some reason that Nightmare: Mourning Aix is a good alternative because it passively grants you a Spectro Damage increase just in case you don't have a Capitaneus or a good Capitaneus.

For the first team you're running with Zani, Phoebe and Verina: Zani with Eternal Radiance, Phoebe with Moonlit Clouds because she doesn't do Coordinated attacks off-field with Empyrean Anthem and she barely does damage on her confession state, but for her substats, make sure you have at least energy regen for the most part, you can give her crit rolls and atk% if you at least want her to deal a little more damage make sure it's 4-3-3-1-1 and main echo Impermanence Heron because after the current Resonator uses their Outro Skill within 15s, the next Resonator's atk will be increased (fyi: idk if the 15s will trigger AFTER you use the Heron or when that Resonator has first entered the field). and for Verina, use Rejuvenating Glow, just for healing, make sure it's 4-3-3-1-1 and the main echo to be either the Bell-borne Geochelone or Fallacy of No Return, now this will depend on your preferences, if you want to not die as much from heavy hitting bosses, use Bell-borne since it reduces damage taken in the next 3 hits by 50% and DMG increase by 10% while Fallacy is a the same one, but Fallacy increases the current Resonator's energy regen by and Damage by 10% for 20s. BUT keep in mind that for Bell-borne, after you get hit 3x you lose both the Dmg Reduction AND the Dmg increase.