Putting up Zach and Amber is a bad move. In fact, putting up Zach and ANYONE is a bad move.
After all, there are three "pairs" in the game now, plus Zach who floats more than the Goodyear Blimp. In order to make it to the final three (and ideally, the final two) you would need to break up BOTH of the other two pairs. To do that, you need to put up both people of a pair, and assure that you have Zach's vote. That way, even if one of the nominees wins POV and takes his/her self off the block, you still have the votes to evict the other one.
For example: Jess nominates Dick and Dani. If neither comes off the block, you've broken up a pair. If one does, you put up someone from the other pair, because with Eric and Zach's vote, it should be 3-1 to eliminate who you want. Even if America screws with Eric's vote, at 2-2 you break the tie. To further ensure her own success, she should get Amber and Zach to agree not to put her and Eric up next week. Amber would put up Zach and the other Donato. Zach would put up (probably) Amber and the other D, or if you got real lucky, Amber and Jameka. Again, you've got two votes, so as long as the remaining Donato doesn't win HOH and put her and Eric up, they get to decide who goes, and then it's Eric/Jess, one Donato, half of Jamber, and Zach. You're the only pair left and should be in control.
Of course, the way this game has worked so far, Dick and Jameka will probably become the best of friends and all your plans go up in smoke.