Moon Dust vs Zombie Flesh

How close are they?

ΔE 17.6, loose: different enough that you should pick on purpose. Zombie Flesh is noticeably darker, cooler than Moon Dust.

Can I use Zombie Flesh instead of Moon Dust?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Zombie Flesh is noticeably darker, cooler than Moon Dust.

Can I use Moon Dust instead of Zombie Flesh?

The same difference applies the other way round: Moon Dust is noticeably lighter, warmer.

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.