Answer
When partial derivative δz/δy is zero for all values of x, this means that z is not a function of y and the total derivative of z with respect to x is equal to partial derivative of z with respect to x.
Work Step by Step
When partial derivative δz/δy is zero for all values of x, this means that z is not a function of y and the total derivative of z with respect to x is equal to partial derivative of z with respect to x.