  A $Z_2$ symmetry that extends the weak interaction, $SU(2)_L \rightarrow
SU(2)_L \times SU(2)'$, and the Higgs sector, $H(2) \rightarrow H(2,1) +
H'(1,2)$, yields a Standard Model quartic coupling that vanishes at scale $v' =
<H'>~\gg~<H>$. Near $v'$, theories either have a "prime" sector, or possess
"Left-Right" (LR) symmetry with $SU(2)' = SU(2)_R$. If the $Z_2$ symmetry
incorporates spacetime parity, these theories can solve the strong CP problem.
The LR theories have all quark and lepton masses arising from operators of
dimension 5 or more, requiring Froggatt-Nielsen structures. Two-loop
contributions to $\bar{\theta}$ are estimated and typically lead to a neutron
electric dipole moment of order $10^{-27}$e cm that can be observed in future
experiments. Minimal models, with gauge group $SU(3) \times SU(2)_L \times
SU(2)_L \times U(1)_{B-L}$, have precise gauge coupling unification for $v' =
10^{10\pm1}$ GeV, successfully correlating gauge unification with the observed
Higgs mass of $125$ GeV. With $SU(3) \times U(1)_{B-L}$ embedded in $SU(4)$,
the central value of the unification scale is reduced from $10^{16-17}$ GeV to
below $10^{16}$ GeV, improving the likelihood of proton decay discovery.
Unified theories based on $SO(10) \times CP$ are constructed that have $H+H'$
in a ${\bf 16}$ or ${\bf 144}$ and generate higher-dimensional flavor
operators, while maintaining perturbative gauge couplings.
