You cannot. && can only be used for scalars.
Note that if you are trying to code something like
if vector1 && vector2
then the "if" would be considered true only if all values in "vector1 && vector2" evaluated to true, because that is how "if" behaves on vectors and matrices, as if there was an all() wrapped around everything:
if all(vector1 && vector2)
With some minor thought on the meaning of "&" you can see this would be the same as
if all(all(vector1) && all(vector2))
which could be written more briefly as
if all(vector1) && all(vector2)
which is allowed.
