Export output to a text file

Here is another version which I think is showing some useful tricks specific to Mathematica:

 data = {
        x[1]->1011.07,y[1]->1127.56,z[1]->420.922, 
        x[2]->940.095,y[2]->1041.71,z[2]->414.793,
        x[3] -> 754.727,y[3]->1088.95,z[3]-> 467.422
 }

 Export[
   FileNameJoin[{$HomeDirectory,"Desktop","data.txt"}],
   Join[
     {{"index", "x", "y", "z"}},
     Table[{i, x[i], y[i], z[i]}, {i, 3}] /. data
   ],
   "Table"
 ]

Some explanations:

• I find it more convenient and less error-prone to work with full path-names when working with files than to rely on the current value of Directory[].
• FileNameJoin and the $*Directory variables are essential tools to work with filenames that I think every Mathematica user should know about.
• There is nothing wrong with using File to specify the filename to export to here, but I think for such relatively simple use cases it is an unnecessary abstraction.
• As you have your data as a list of rules it seems easiest to take advantage of that fact when constructing the tabular data you are after.
• I could have used Prepend instead of Join which would have saved me the extra pair of curly brackets, but I find it more clear to write the header before the data in such cases...

If this is really the structure, maybe you could use a dataset instead?

pdata = Partition[coord/. h_[i_Integer] -> h, 3]
ds = Dataset[Association @@@ pdata]

Indexes are supplied automatically. E.g.,

ds[[1]]

Here is an approach that address the core of your request

First strip the values from the Association and group them with Partition.

z1 = Values[coord] // Partition[#, 3] & ;

Now create a file variable

theFile = File["exportFile.txt"];

Export as follows (using "Table" argument to Export

Export[theFile, z1, "Table"];

This file will end up in the directory referred to by Directory[]

---x---

Now a little more complication

Add a columns of row indices to the left of your table with (I think it is convoluted syntax, but it works....)

z2 = Insert[z1 // Transpose, Range[3], 1] // Transpose;

The next picture shows z1 and z2.

Add a row of labels to the top of your table

z3 = Prepend[z2, {"index", "x", "y", "z"}];

And then Export the variable z3 instead of z1 as above.

The only problem is the labels aren't aligned properly; this could be a problem or not; depending on how you will use the exported file.