Zamesi Desert vs Medium Yellow

How close are they?

ΔE 18.2, loose: different enough that you should pick on purpose. Medium Yellow is a little lighter, much more saturated than Zamesi Desert.

Can I use Medium Yellow instead of Zamesi Desert?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Medium Yellow is a little lighter, much more saturated than Zamesi Desert.

Can I use Zamesi Desert instead of Medium Yellow?

The same difference applies the other way round: Zamesi Desert is a little darker, much more muted.

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.