What is the difference between Cha Cha Walk and Rumba Walk (in term of technique)?
It is very appreciated if any one can make it clear.

I do not think no one know this

Please read this version and discard the prior one there are some typos in the prior version:

No difference except you have less time in CC for a beat (approx.: half a second) than in CC. The walk is normally considered a full beat, as opposed to the step which is normally a half beat, and the entire look of motion should be different than the walk. (There are teaching videos on this.)

The foot speed is the same in forward walk (in CC and R) your foot (not your body) arrives on the floor on the beat. On backward walk you put down your heel on the beat (full body weight not yet transferred).