Description of the low-lying collective states of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Zr</mml:mi><mml:mprescripts /><mml:none /><mml:mn>96</mml:mn></mml:mmultiscripts></mml:math> based on the collective Bohr Hamiltonian including the triaxiality degree of freedom