Is better to say the e.g. kinetic energy is 0 joule or kinetic energy is 0 ? since 0*joule equals 0.Is a mathematical concept behind because in many books i find both ways.
Fools rush in where angels fear to tread, but I think it's usual to leave out the unit, on the grounds that zero KE is zero of whatever units we use: joule, erg, foot pound weight, foot poundal…
Then there's the argument that units are to be treated as algebraic symbols, so 50 J means 50 multiplied by J and 0 J is zero multiplied by J, which is simply 0.