ΔE 20.9, loose: different enough that you should pick on purpose. Steel Grey is a little lighter, much more muted than Zima Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Steel Grey is a little lighter, much more muted than Zima Blue.
The same difference applies the other way round: Zima Blue is a little darker, much 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 Zima Blue on the colour wheel See Steel Grey on the colour wheel
All matches: Zima Blue equivalents · Steel Grey equivalents