Light Yellow vs Zamesi Desert

How close are they?

ΔE 17.9, loose: different enough that you should pick on purpose. Zamesi Desert is a little darker, warmer than Light Yellow.

Can I use Zamesi Desert instead of Light Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Zamesi Desert is a little darker, warmer than Light Yellow.

Can I use Light Yellow instead of Zamesi Desert?

The same difference applies the other way round: Light Yellow is a little lighter, cooler.

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.