ΔE 28.5, loose: different enough that you should pick on purpose. Chromium Oxide Green is noticeably darker, much more muted, cooler than Nurgle's Rot. They are different kinds of paint: Citadel Nurgle's Rot is a technical paint or medium and Golden Chromium Oxide Green is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Chromium Oxide Green is noticeably darker, much more muted, cooler than Nurgle's Rot. They are different kinds of paint.
The same difference applies the other way round: Nurgle's Rot is noticeably lighter, much more saturated, 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.
See Nurgle's Rot on the colour wheel See Chromium Oxide Green on the colour wheel
All matches: Nurgle's Rot equivalents · Chromium Oxide Green equivalents