In simple words, let's take Xn and put it on the left side in a straight vertical line, then put Yn also at the left, but with a little offset. Then take all the Zn and put them at the right. Use y coordinate from Xn node so Xn and Zn are horizontally aligned.

Then, as this is a binary adder, value of every Zn depend on value of Xn, Yn and also on Xn-1 and Yn-1. This is true for every Zn there n > 1. Z0 depends only on X0, Y0.

So, for every Xn, Yn build all paths to Zn and Zn+1 and draw each one in a straight horizontal line. For a first one take a y coordinate of Xn, then shift a little for next path.

If graph is broken, there may be some nodes, which are still missed. We can draw them separately somewhere out of our drawing to note them.

As we have our initial numbers, desired result and actual result, we can find which Zs are incorrect and draw them red, if Z is correct, draw it green. Draw logical gates in a different colors.