Cross symmetry between pairs
The two interlocking pairs of chapters (40, 89) and (21, 90) display a reciprocal symmetry, where, the product of one pair is the verse span of the other! (top two arrows). The verse span from 40 to 89 is 21 × 90 and symmetrically, the verse span from 21 to 90 is 40 × 89! Likewise, the two pairs (20, 92) and (41, 91) from the two bottom arrows are mutually cross linked via their verse spans, which are, at the same time, the products from their counterparts.
The curved, dotted arrows provide additional links between upper and lower pairs as 20 and 21 are the verses of 90 and 92, respectively.