The current military operation can arguably accomplish both of these tasks (the first one much more easily than the second). However, while Israel has a clear right to protect its citizens, the question that needs to be asked is: Are the costs of a further escalation and of a possible ground operation worth it for Israel, and how much time can it buy?
The first obvious cost of the ongoing escalation rests within the civilian population in both Israel and Gaza, who are paying directly for the resumption of major hostilities.
Israel appears to be confident it can bear the military costs of the operation. But this assumption is largely shaped by the awareness that the conflict is unlikely to expand to a region-wide war. Iran is dealing with crippling sanctions, Syria is in the midst of a civil war, and Hezbollah’s power has been diminished by its siding with its Syrian patron, the Bashar al-Assad regime. So it is unlikely that any of these parties will get directly involved in the fighting in Gaza.
However, Israel should not disregard the political and diplomatic consequences of continued escalation. The already frail and shaky relationship with Egypt is a first obvious casualty of the current situation, with the future of bilateral relations and the peace treaty with Egypt looking ever colder.
Israel's overall position in the region also suffers as a result of the ongoing military operations. This is particularly the case since – as a result of the "Arab awakening" and the increased weight of the "Arab street" in the region – there is greater pressure on regional players to openly condemn Israel and to support Hamas in Gaza. And the more protracted and extensive the operations will be, the more the country's standing and legitimacy will suffer at the international level, even among Israel’s western allies.