  The low-lying states in 106Zr and 108Zr have been investigated by means of
{\beta}-{\gamma} and isomer spectroscopy at the RI beam factory, respectively.
A new isomer with a half-life of 620\pm150 ns has been identified in 108Zr. For
the sequence of even-even Zr isotopes, the excitation energies of the first 2+
states reach a minimum at N = 64 and gradually increase as the neutron number
increases up to N = 68, suggesting a deformed sub-shell closure at N = 64. The
deformed ground state of 108Zr indicates that a spherical sub-shell gap
predicted at N = 70 is not large enough to change the ground state of 108Zr to
the spherical shape. The possibility of a tetrahedral shape isomer in 108Zr is
also discussed.
