public static Either <IEnumerable <TResult>, TRight> Zip <T1, T2, TResult, TRight>(
IEnumerable <T1> first,
IEnumerable <T2> second,
Func <T1, T2, Either <TResult, TRight> > resultSelector)
=> Either.Collect(first.Zip(second, resultSelector));
public static Either <IEnumerable <TResult>, TRight> Map <T, TResult, TRight>(
IEnumerable <T> source,
Func <T, Either <TResult, TRight> > selector)
=> Either.Collect(source.Select(selector));