If Zach were really smart, he would look around, and see
(a) Eric and Jess are a pair
(b) Dick and Dani are a pair
(c) Jameka is on her own
(d) HE is on his own.
Make nice with Jameka, put the past behind them, blah blah, and nominate Dick and Eric.
If one of the two comes down, he puts up either (a) the other nominee's partner, or (b) the off-the-block nominee's partner. Then one of the pairs is broken up for sure.
The danger is, with Jameka not able to play for HOH, that he and Jameka both go up next week. But even then, he's got a better chance of staying because no one wants to be next to Jameka in the final 2.