you divide by 6 and take the remainder

e.g.

5 x 5 = 25

25 divided by 6 = 4 remainder 1

you only need the '1', as in the table

although some of the values in the 'x' table look wrong, for example 1 x 1 = 1 , not 2 as in the table

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note also your question asks for z/6, but your tables are z/6

so for z/8, work out then divide by 8, and keep the remainder