The most compatible signs with Libra are generally considered to be Gemini, Leo, Sagittarius, and Aquarius. Efron also dated the daughter of Bruce Willis and Demi Moore, Rumor Willis. They split a couple of months later due to busy schedules but reunited in October 2013.
The official word from both of the actors' camps is that nothing is going on; Alexandra told E!'s own Jason Kennedy at this weekend's Billboard Music Awards that "I understand why people would go crazy over something like that, but Zac and I are very good friends." But that doesn't exactly explain the straight-up deluge of content the two are throwing up; it leads any millennial to think that they've gone If Zac and Alexandra really are doing the horizontal limbo, or a more romantic version of it, then it would have all started on the Miami set.