How to replace-regexp by the average?

[gnuist006@gmail.com]

Given strings of this type

TOKEN 123.456 12.3456 1234.56

replace by

TOKEN 67.9008 623.453

where the first number is the average, ie what you get from the evaluation of

(/ (+ 123.456 12.3456) 2.0)

and second is also the average, ditto

(/ (+ 1234.56 12.3456) 2.0)

both upto 6 significant digits.

I tried this but it does not work.

(save-excursion (replace-regexp "TOKEN \\([0-9\\.]+\\) \\([0-9\\.]+\\) \\([0-9\\.]+\\)" (concat "TOKEN (format "6.6f" (/ (+ \\1 \\2) 2.0)) (format "6.6f" (/ (+ \\2 \\3) 2.0)) ) ))

Any help in improving while keeping it readable one-liner sexp and maintaining the use of \\1 \\2 \\3 etc if possible ... ?

Cheers,
Bolega