Why are Israel and Pakistan fighting over Gaza Strip?

Answer 1

Israel and Pakistan have no diplomatic relations, but are not currently in a State of War. Pakistan has not attempted, militarily or politically, to prevent Israeli or Palestinian interests from being realized in the Gaza Strip.

If instead of Pakistan, you meant Palestine, please see the Related Question.

Answer 2

The fighting in the West Bank and the Gaza Strip are completely different.

Currently, the West Bank is occupied, but not being actively fought over. It is a disputed territory and both the Israeli Government and the Palestinian Authority are jockeying to control some or all of that region in the future. At this point it is mostly about whether or not the Israeli Settlers should be removed, whether the Checkpoints are necessary, and Palestinian Rights to Land and Jobs.

The Gaza Strip is currently ruled by Hamas which is dead-set on opposing the Israeli Right to Exist. It has constantly bombarded Israeli cities close to it and recently expanded its firing range to the Israeli financial capital of Tel Aviv. The Israelis have surrounded Gaza with a blockade and armed border to prevent the influx of the very missiles used to perpetrate these attacks. This has caused a humanitarian problem in Gaza, resulting in increased fury to attack the Israelis. This vicious cycle self-perpetuates.