Build concept (may vary according to your riven; I don't recommend using Zenith rivenless):

• Amalgam Serration for damage and archwing speed.
• Critical Delay to hit > 100% crit chance.
• Vital Sense for crit damage.
• Hellfire to combine with Shock Trooper.
• Three fire rate mods for faster water limbs.

In practise:

• Get Roar buff from VS.
• Stack Primary Deadhead before Teralyst/Gantulyst capshots if you have time (doing the capshot with [Zenith] can give another stack, if you don't need a faster capshot to hit a shrine breakpoint). The damage generally is not needed, but Eclipse lighting tends to be worse at the beginning and end of the night cycle, and doesn't hurt - particularly if VS is not running a high strength build for Roar.
• Pick up Electric Shield before entering archwing to shard for the crit damage bonus.
• Shoot Zenith disk over the lake before Gantulyst/Hydrolyst spawn to be sure that it doesn't switch back to auto mode (this happens when you move more than ~250m away from where the disk lands).
• Proc vig swap for Twitch/Reflex Draw to reduce recoil/pellet spread (this is faster by using the Synthesis Scanner than actually swapping weapons).
• Use scanner if you lack x-ray vision to see through the hill at long spawn and VS doesn't take the limb.
• Pray for no close left spawns if hosting [Nova] 🙃