"Null" and "nil" have very specific uses (maths and sport respectively) as well as set phrases, eg. "null and void"(legal) and "nil by mouth" (medical). "Zero" is the more general word.

In normal speech and writing, NULL is never used. It does have uses in computer programming. NIL is generally only used in sports, and only in the UK/Australia. For all normal purposes, ZERO should be used.

Hello! Peachey teacher and Rossa_arie. =D Thank you very much for helping me. Have a nice day .! =D=D