HoDoKu W-Wing

The cells {2} and {3} <-> {0} and {1} form a W-Wing pattern on the values {4} and {5}.

In {6} there are only two cells ({2} and {3}) which may be {5}, so one of those two cells must contain the value {5}, and those two cells also have two siblings ({0} and {1}) which can only be {4} or {5}, therefore one of those two siblings must contain the value {4}, therefore any cells that are siblings of both the siblings {0} and {1} may not be {4}.

Other occurrences of the value {4} can therefore be removed from siblings of both {0} and {1}, ie {7}.