ME:
1) I grant that the letters A,B,C,D and H have property ZINGER
2) I grant that all roman alphabet letters both upper case and lowercase have property ZINGER

YOU:
But what about L,M,N,O,P, do they have property ZINGER? You must have omitted these for some reason they must Not have property ZINGER!

SOLUTION:

{ A, B, C, D, H } Union (Roman Alphabet) = Roman Alphabet.

L,M,N,O,P are letters in the set Roman Alphabet and hence also have property ZINGER.

QED.