This scenario or anything similar would quickly lead to nuclear war. Iran, Syria, Egypt, Turkey and Lebanon would take it as their cue to attack Israel. The missile bombardment of Israeli cities by these players would lead inexorably to the use of nuclear weapons by Israel against military targets in several ME countries and be quickly followed by nuclear strikes on several cities. In such a conflagration Israeli forces would take a dim view of any UN peacekeeping forces and would attack any such forces unmercifully. The IDF is not in any way similar to the weak forces of other ME nations that UN forces have come up against before.
No one can defeat Israel, the absolute best that could ever be achieved would be to die along with her. Only maniacs attack nations with strategic thermonuclear capabilities.
Israel is nuclear-armed. But thermonuclear? I've never heard. That is a quantum leap in destructiveness, up into the megaton range. (The kiloton range is bad enough, ask the Japanese .... and the bombs they saw were at the low end of what is called tactical yield these days.)