I think the only downgrade the ZR has taken over Z and ZL is the screen size and move from HD to 720p. In fact, it has a similar battery, that too a user replaceable one. GSMarena gave ZR a 62hr rating compared to the 48hrs of the Z. Also, Mugen power has launched a 88$ 4600mah powerpack for ZR that promises double the power of the original. Mindblowing!