Ming would have to bulk up way too much to handle Shaq. But what Ming would do, out of pure height and his fairly decent stature (i.e. not Shawn Bradley), is make Shaq work for every shot down low. Shaq's 8-foot hook shot and basically anything outside of the ring under the rim will be very tough to get off against Ming, assuming his defense and footwork are NBA average. Shaq can and will definitely overpower Ming, for as long as they play, and that will be the ridiculous advantage for Shaq's side, but that is a difficult one.
One way to look at it: Ming will throw Shaq back into the days of the Orlando Magic, when his moves were not nearly as polished but his size enabled him to average ridiculous amounts of points and boards anyway. That was not an unstoppable Shaq; that was a NEARLY unstoppable Shaq.
Of course, Ming will never win this fight. But if teams like Milwaukee, Sacramento, Dallas, or Orlando had Ming, they would feel comfortable using him one on one against Shaq. In Houston, the SF position needs a significant upgrade. Francis, Mobley, Griffin, and Ming are the current and future stars of this team... with one missing piece (possibly Nachbar, if he develops), the team could rely solely on the rugged defense on the wings and on the weak side to leave Ming with Shaq one on one. And that is not something anyone can say in the NBA.
Shaq will always score 20+ points against Ming. But he'll exert a lot of energy for them, and it may be to the Rockets benefit if he has to shift his hulk around on his two bad feet...