I’m going to suggest the same things as your other question Renewable generation constraint.
incidence = [1 -1 0 0; 0 1 -1 0; 0 1 0 -1; 1 0 0 -1]
This is a Matrix. You index it as incidence[row, column].
sum(incidence[z][l] * vVoltag
But here you indexed it as incidence[z][l]. It should probably be incidence[z, l].
Since both questions have been small typos, you should carefully checking each part of what you write.