White Maximummer = White has to make his longest move (as measured between the centres of the both squares.) If he is in check he has to make his longest move that avoids check.
Zero-position = the position you see is really no puzzle in itself. To make a problem position out of it you'll have to make one of the (minor) changes mentioned (e.g. a: diagram position except that pawn c4 should be on d3 etc.)