Since they were born within a few days of each other, Mandy and Zach have their Suns a few degrees apart in Aries, which right away shows their core personalities are similar. Zach's Mercury (communication) in Aries is almost exactly conjunct Mandy's Venus (relationships and values), and conversely, while Zach's Venus and Mandy's Mercury are not conjunct, they are both in Taurus.
As happens all too often with these pesky privacy-craving public figures, I am stymied by lack of an exact birth time for either party, and hence inability to determine the relationship of their two Moons, which describes how they relate emotionally. But whether or not their Moons are in contact by aspect, they are likely in opposite signs (Mandy, Leo; Zach, Aquarius), which is always a good indicator for a romantic connection, as opposite Moon signs balance each other emotionally.
So, this couple seems to be pretty darn simpatico, and with Mandy's Jupiter (growth and expansion) in ambitious Capricorn opposite Zach's Saturn, there may be serious long-term commitment potential here. Saturn contacts between two charts tend to suggest a binding, enduring connection between two people. However, there is some chance this contact could go the other way, with Zach feeling defensive and protective about Mandy's eagerness to settle down for the long haul. Her Saturn in Aries inconjuncts his Sun in Aries, which suggests that to make a deep emotional commitment to her, he will need to make some adjustments to his independent, do-whatever-he-wants lifestyle. (For a dorky-looking guy, he seems to have quite a way with the ladies. With Mercury conjunct Jupiter, he must be able to seduce them with his doesn't-miss-a-beat wit and a healthy dose of cockiness.)
My main concern about Zach and Mandy's endurance potential is that they may be too similar. Aries really, really like getting their own way, and, in case you were wondering, they equally dislike not getting their own way. Two Aries together will get along great as long as they're headed in the same direction by choice. But as soon as they want different things, two Rams will tend to butt heads. Compromise is not a concept that comes naturally to them.
Now, in Zach and Mandy's composite chart, the Sun, Mercury and Venus are all together in Aries, which again means that when they present a united front they're almost unstoppable -- but if there are any divisive points between them, they may be unable to work toward a compromise. Aries are also known for being impulsive and impetuous, better at starting new projects than seeing them through, and it may be that Mandy and Zach, as a couple, don't have the perseverance to stick it out through the work it takes to build a lasting relationship.
Biased as this may sound coming from someone who plays for the Bulls (in the zodiacal sense, as opposed to the sense of being tall and having hand-eye coordination), it's their Taurus planets that could save them -- with Zach's Venus in Taurus, he is loyal and craves security when it comes to relationships, while Mandy's Mercury in Taurus gives her a bit more patience and willingness to talk things out than the average Aries. In the composite chart, the Moon is almost certainly in Taurus, although its exact position cannot be pinned down due to their uncertain birth times. It may be that their emotional commitment to each other is deep enough to sustain them through the Aries flare-ups… or it could be that neither Ram has the dedication to stick it out with someone who's equally strong-willed, opinionated and temper-prone. If anyone happens to know Zach's or Mandy's birth time, puh-leeeeze email me, as the Moon aspects and rising signs could be make-or-break factors for this couple. Mandy, if you're reading this, call your mom ASAP and ask her to check your birth certificate. I just want you to be happy!
