∆z[j]+= max(∆z[j],0)

Hello, I would like to ask how to represent this in CVX, only take the number greater than 0, and the others are equal to 0;

Have you looked at pos and max?

If that doesn’t suffice to enable you to express this in CVX, can you write that out in explicit (regular) MATLAB code (pretending everything were double precision MATLAB variables). I don’t understand what that notation means.