Hint

The second letter of word V1 has to be the same as the second letter of word H1, the fourth letter of word V1 has to be the same as the second letter of word H2, and the sixth letter of word V1 has to be the same as the second letter of word H3. Similar constraints can be specified for the other words, as illustrated by this picture.

If all of these constraints are satisfied, then the predicate crossword/6 should succeed.

Solution

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