ΔE 7.3, close: similar, with a visible difference side by side. Zinc White is a little lighter, more muted than Skyshard.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Zinc White is a little lighter, more muted than Skyshard.
The same difference applies the other way round: Skyshard is a little darker, more saturated.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Skyshard on the colour wheel See Zinc White on the colour wheel
All matches: Skyshard equivalents · Zinc White equivalents