Since DA is the diameter, this means that you can divide the circle into two half-circles. You will solve with the right half-circle. A half-circle has a 180 total degrees. Add up the values given and solve for x.
(2x) + (7x - 4) + (85) = 180
2x + 7x - 4 + 85 = 180
9x - 4 + 85 = 180
9x + 81 = 180
9x = 99
x = 11
Now that you have the value of x, solve for m∠CZB.
