The wire is broken because you cannot connect that datatype to either of those two functions. The source datatype is a 1D array of clusters, where each cluster contains two arrays. The Write Text File accepts strings, not clusters. The Write to Measurement File accepts dynamic data, and while you can convert arrays to dynamic data, there is no built-in mechanism to convert a 1D array of clusters of two arrays.
What you'd need to do is to convert the data into a format that can be accepted by these functions. Since you want to have a "spreadsheet" file then you should use Write to Spreadsheet File which creates a delimited text file. Since the frequency data would be the same for the magnitude plot and the phase plot you can have 3 columns: frequency, magnitude, and phase. You can peel off the elements using Unbundle by Name and then create a 2D array from each cluster element. The real question is whether you want to save the data at each iteration and whether you are just adding onto the file. The attached figure shows writing out an initial header and then just continuously adding to the data.
