What purpose does the soft shackle serve? I'm not familiar with soft shackles being used in either hammock or tarp ridgelines.
Some folks (like me) use soft shackle prusiks to attach tarp to tarp ridgeline. Yes, you can use the same diameter Zing-it for your soft shackle prusiks, but you may need to go four wraps instead of three on the prusik. Once the coating wears off they shouldn't slip.
As for a hammock ridgeline, mine is adjustable. I use a 1.75 mm Zing-It whoopie sling. The fixed loop of the whoopie is larksheaded to the continuous loop running through the hammock end-channel. The adjustable loop of the whoopie connects to a titanium Dutch ridgeline biner, which connects to the continuous loop on the other end of the hammock.
Instead of a biner, you could use a soft shackle.