Among three bases, x−, y−, and z−, the strongest one is y−, and the weakest one is z−. rank their conjugate acids, hx, hy, and hz, in order of decreasing strength.

Bases:
x-     middle strength
y-     strongest base
z-     weakest base

The bases and conjugate acids have an inverse strength. The stronger the conjugate base, the weaker its conjugate acid. 

I am considering two scenarios:
Scenario 1:
y- strongest base ; hy - weakest conjugate acid
x- middle base ; hx - middle conjugate acid
z- weakest base ; hz - strongest conjugate acid

hz → hx → hy

Scenario 2:
y-strongest base ; hy - weakest conjugate acid
x-middle base ; hx - strongest conjugate acid
z-weakest base ; hz - middle conjugate acid

hx → hz → hy