Regular expression,

Question

Question 23: The string zyyzy belong to the language, right?

Answer 1

$zyyzy$ does belong to the language but not $zyyxz$

Edit : in $zyyzy$ can be split into two : $zyy$ and $zy$ which both belongs to $zy^*$ and therefore $zyyzy$ belongs to $(x^*y|zy^*)^*$