their hard and thankless work in developing it properly
This is the Zionist claim that I have the hardest time swallowing for the simple reason it is the same bunk every other group of European colonialists used to justify their colonies. The fact that Zionism happened to be an European colonialist ideology centered around a group of European colonialists who could trace their ancestors to having once lived in the area they proposed to colonize doesn't justify it in my opinion.
That said, regardless of whether the State of Israel should've been created is a pointless argument. It does exist, and the Israelis there exist, just as the Palestinians exist, and no peace is possible unless all sides admit those basic facts and accept the resulting implications of those facts.