The initial part of the sequence will begin with Searing Light weaved immediately, followed by a buffer Ruin III before Demi-Bahamut is summoned. This is due to the assumption of a 2.46s GCD tier, as this Ruin III will inevitably occur due to the spell speed scaling interaction on the trance cooldown.
The fight timeline will allow you to delay your Energy Drain in the opener, aligning an additional 200 potency into raid buffs. Along with this, remember to align your Deathflare, Enkindle Bahamut, and Festers for the full raid buff window as well.
Following the opening Bahamut, your opening sequence will continue into the primal phase. Depending on your party composition, you will have two possible choices to make for optimal damage gains:
Opener - Primal Phase (Titan first)
With this opener option, you will prioritize using Titan as your first primal summon, followed by Garuda with a swiftcasted Slipstream to snapshot the tail end of your Tincture duration. This opener option will generally be your preferred sequence, especially in the presence of 20 second raid buffs such as Embolden and Technical Finish.
The first phase of the encounter will provide full uptime until ~2:57, meaning your rotation alignment throughout this phase will follow standard practices. During this time, you will have 3 trance timings in total, as well as a total of 9 primal summons.
There is only one unique consideration to make with regards to your rotation during this phase. With the 3rd set of primals following your 2nd Bahamut timing, make sure that Garuda is never used as the final primal. With the timing of Zodiark going untargetable at ~2:57, using Garuda last would compromise on the remaining duration of your Slipstream DoT puddle. Therefore, using Garuda earlier will avoid this problem from arising.
As this encounter will allow you to delay the use of Energy Drain for raid buff windows, this will also provide the opportunity to hold Aetherflow Gauge as well. For Zodiark specifically, this entails holding the Aetherflow Gauge generated during your Phoenix durations, to be later used with your Searing Light and other 120s party buffs.