By Eliot's later work, this is almost certainly referring to Four Quartets, Eliot's most post-modern poem.
See: T. S. Eliot bibliography > Poetry
If you've read a lot of Eliot, there is a great deal of evolution between Prufrock (1917) and the Quartets (1940-43). Rather than attempting a breakdown of the differences between the Wasteland (1921) and the Quartets, I'll use an example of the convolutional passages that feature strongly in the latter work. The Quartets begin:
Time present and time past are both perhaps present in time future, and time future contained in time past. If all time is eternally present, all time is unredeemable. What might have been is an abstraction, remaining a perpetual possibility only in a world of speculation. What might have been and what have been point to one end, which is always present.
The meter of the Hughes excerpt seems a direct reference to "time before and time after", featured in part III of Burnt Norton:
Here is a place of disaffection
Time before and time after
In a dim light: neither daylight
Investing form with lucid stillness
Turning shadow into transient beauty
With slow rotation suggesting permanence
Nor darkness to purify the soul
Emptying the sensual with deprivation
Cleansing affection from the temporal.
Neither plenitude nor vacancy. Only a flicker
Over the strained time-ridden faces
Distracted from distraction by distraction
Filled with fancies and empty of meaning
Tumid apathy with no concentration
Men and bits of paper, whirled by the cold wind
That blows before and after time,
Wind in and out of unwholesome lungs
Time before and time after.
Although, the Hughes passage feels more in the spirit of the Hollow Men (1925): "Shape without form, shade without colour, paralysed force, gesture without motion".
"Cipher" in the Hughes relates to the layers and layers of meaning in Four Quartets, which is closer to the "neurolinguistic code" some very smart people have used in reference to Finnegan's Wake.
For Eliot, this is partly a function of:
"The intolerable wrestle with words and meanings"
Hughes' The Crow is regarded partly as an attack on Christianity, where both the Wasteland and Four Quartets can be understood as an attempt to reconcile Western and Eastern religious ideals. (Specifically Christianity and Hinduism.)
The Hughes society also categorizes Crow as an attack on humanism
It was his most controversial work: a stylistic experiment which abandoned many of the attractive features of his earlier work, and an ideological challenge to both Christianity and humanism.
Eliot's work, by contrast, is highly humanistic. If you're interested in this theme in Hughes, I'd highly recommend the poetry of Robinson Jeffers, who precedes Hughes, per Jeffers' central theme of inhumanity.