Obviously the four corners are what I was referring to.
What you have said here is that the four furthest parts of the world from wherever the prophetic events are set "would be considered corners". Even you are not claiming that the world has literal corners. Rather, you are hypothesising that there are regions of the world that are "considered" corners - in other words, figuratively referred to using the word "corner", even though they are not literal corners.
In fact, your own interpretation of those two passages is equally consistent with both a spherical earth and a round one, given neither has literal corners, but both would have four regions of the world that were the four furthest from the events in question.
My point is that here are two verses that very clearly, if taken literally, describe a square earth. Yet neither of us believes the earth is literally square. Just because a prophetic verse is written in a way that implies a certain shape of the world does not mean the world actually is that shape. These prophecies use figures of speech. And other prophetic passages may also.
Again, here we have some prophesied events that seem to imply a particular structure for the world - that somehow everyone will be able to see Jesus simultaneously. But as I stated earlier, this is a physical impossibility in either a round or flat earth model.
Can you see lightning in the sky above Jerusalem from wherever you live? If not, how would you see Jesus in the sky there from where you live either? You could not, without some form of supernatural bending of whatever laws of physics prevents you from seeing the sky above Jerusalem today.
Therefore, these verses are not describing something that occurs somewhere that everyone can physically see in normal circumstances - no such place exists. A different interpretation must be chosen. Several are possible:
- Everyone will see him in the sky immediately due to a supernatural alteration of the laws of physics allowing distant events to be seen everywhere.
- Everyone will see him in the sky immediately through human technology - televisions, video streaming and so forth.
- Note very carefully the wording of those verses. The following suggestion is actually completely consistent with the words used: Everyone will not see him immediately. Rather, everyone will see "the sign of the Son of man in heaven" (whatever that is - think of a comet, everyone can see it, just not all at once, but within a day everyone will have had a view of it). Then he will come in the clouds, and some people will see him doing that, followed by everyone seeing him as he travels around the world doing stuff.
Other interpretations may be possible, I honestly don't know which is correct. But my point is that these verses are not explained by the earth being flat. You are still left with the problem that the sky above Jerusalem is not visible from the entire world. That problem must be resolved in a different way (I've suggested three possible options).
This does not show the earth is flat because the earth being flat doesn't actually explain the prophecy.