Zombie Flesh vs N8 Neutral Gray

How close are they?

ΔE 18.6, loose: different enough that you should pick on purpose. N8 Neutral Gray is a little lighter, much more muted than Zombie Flesh.

Can I use N8 Neutral Gray instead of Zombie Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). N8 Neutral Gray is a little lighter, much more muted than Zombie Flesh.

Can I use Zombie Flesh instead of N8 Neutral Gray?

The same difference applies the other way round: Zombie Flesh 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.