Singleton Zoolock

Unfortunately, there's no way to tutor Zephrys.

In a zoo deck, Zephrys can provide very powerful burn cards such as fireball, bloodlust, leeroy jenkins, soulfire, etc. In addition, just as a 2 drop, he can provide strong 3 drops that zoo normally lacks such as animal companion.

Building singleton zoo is actually not that hard. There are many cards that are good but not good enough that don't make normal zoo lists, such as soulfire.