  Half-filled Landau levels host an emergent Fermi-liquid which displays an
instability towards pairing, culminating in a gapped even-denominator
fractional quantum Hall ground state. While this pairing may be probed by
tuning the polarization of carriers in competing orbital and spin degrees of
freedom, sufficiently high quality platforms offering such tunability remain
few. Here we explore the ground states at filling factor $\nu$ = 5/2 in
ZnO-based two-dimensional electron systems through a forced intersection of
opposing spin branches of Landau levels taking quantum numbers $N$ = 1 and 0.
We reveal a cascade of phases with distinct magnetotransport features including
a gapped phase polarized in the $N$ = 1 level and a compressible phase in N =
0, along with an unexpected Fermi-liquid, a second gapped, and a strongly
anisotropic nematic-like phase at intermediate polarizations when the levels
are near degeneracy. The phase diagram is produced by analyzing the proximity
of the intersecting levels and highlights the excellent reproducibility and
controllability ZnO offers for exploring exotic fractionalized electronic
phases.
