Why is this such an important issue ?
So far as I know (and I have no reason to believe otherwise) - The Army does not discriminate against anyone on the basis of religion, sect or ethnicity; an admirable thing in a country where most other institutions don't always measure up to the high standards we expect them to.
On a side note I do recall listening to a talk-show where one of the journalists mentioned that during Zia's time the Saudis has requested a contingent comprising only of Sunnis and the Army rejected that offer. I do recall another person in the same show corroborating that and none discrediting this piece of information.
Maybe Zia isn't the demon we make him out to be....maybe the demon is misgovernance, apathy and a culture of
'yeh tou Pakistan hai...yahan hotaa hiii yeh hai' statements being made to rationalize all our own personal wrong-doings !