ΔE 15.9, loose: different enough that you should pick on purpose. Zombie Flesh is noticeably darker than Hexos Palesun.
Can I use Zombie Flesh instead of Hexos Palesun?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Zombie Flesh is noticeably darker than Hexos Palesun.
Can I use Hexos Palesun instead of Zombie Flesh?
The same difference applies the other way round: Hexos Palesun is noticeably lighter.
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.