The presence of Jews in that area of the Middle East goes back over 3000 years until the expulsions. People don't dispute that modern-day Palestinians lived there prior to the 1940s - but people conveniently set arbitrary time limits of settlement to allow for one genocide and decry the other.
Politics in the middle east is not a simple case of "Israel bad." Both groups of people deserve a home and both are going to lose part of their national identity regardless of the outcome. A two state solution is the most prudent solution and arguing otherwise ignores reality.
I guess the point wasn't clear enough: Israelis and Palestinians both claim the land due to ancestry. Reasonable people understand the issue is complicated; displacement was a friendly replacement for massacred, forcibly removed, and slavery. You can clearly see that the intent of the creation of Israel was to redress a wrong perpetuated over millennia, regardless of the reality that it caused another migration of peoples.
Like you said, Zionism is just the belief in a divine ancestral claim (core, even, for Judaism) to the region. You can be flippant about it being based in religion and dismiss it from your position of privilege behind a keyboard, but there are radical religious people that believe the land is their birthright just as strongly as some Palestinians and are fighting over that. The religious extremists on both sides of the conflict frankly don't care about your opinions. A two state solution offers the best course for peace in the area, but the extremists from both sides need to be isolated and dealt with. Most Israelis and Palestinians are good people such in the middle of a shitty situation.