Assuming that you also want z[k] = 0 to imply that x[i,j,k] = 0 and y[i,k] = 0, you can impose the following:
con time_constraints_A {k in VEHICLES}:
sum{i in LOCATIONS, j in LOCATIONS} t_A[i, j] * x[i, j, k]
+ sum{i in LOCATIONS} s_A[i] * y[i, k] <= max_time[k] * z[k];
For the second constraint, here is correct syntax:
con type_link {i in LOCATIONS, j in LOCATIONS, k in VEHICLES}:
v_A[i] * z[k] + v_B[i] * (1 - z[k]) >= x[i, j, k];