When you declare a CVX variable, that variable has no relation to a previously defined MATLAB variable of the same name. Your objective function either consists of norm of CVX variable, not tied or constrained to anything else, or is the norm of a constant (i.e., MATLAB variable, not CVX variable), and therefore not affecting the argmin. Your supposed constraint on Z is not a CVX constraint, because it only involves a MATLAB variablle, and not a CVX variable or expression; and so it will evaluate to vector of 0 and 1 (in this case all 1 given your Z), but have no bearing on your optimization problem.
You are allowed to use norm as you have, but U doubt it is doing what you want or need.
You may need modeling help, which you should obtain elsewhere. And I think you need to carefully read the CVX Users’ Guide. I think you need to better learn the basics of MATLAB as well, which you should probably do before trying to learn CVX.