Not exactly. Context defines the meaning.
... then we have to find a time in history before 70AD when 2/3rds of the Church was "slaughtered."
More silliness.
... But Jesus warned the Christians to flee Jerusalem so they would NOT get slaughtered. And they listened to Him.
By "Christians" in this context I assume you mean "Jewish believers in Messiah Jesus". That's who Jesus was speaking to in Matthew 24. They are the ones told to "flee to the mountains". (Which they did, BTW. Your futurist friends would have been telling them to stay put cuz the "great tribulation" wasn't going to happen for at least another 2000 years. "Don't worry, this Rome thing will all blow over.")
Josephus, (not a Christian source), records that the dead in Jerusalem numbered over one million souls.
Now the number of those that were carried captive during the whole war was collected to be ninety-seven thousand ; as was the number of those that perished during the whole siege, eleven hundred thousand, the greater part of whom were indeed of the same nation, [with the citizens of Jerusalem,] but not belonging to the city itself; for they were come up from all the country to the feast of unleavened bread, and were on a sudden shut up by an army , which, at the very first, occasioned so great a straitness among them, that there came a pestilential destruction upon them, and soon afterward such a famine as destroyed them more suddenly.That number is greater than the normal population of the city, but he goes on to estimate the population because of the feasts could at times get as high at "two millions seven hundred thousand and two hundred persons that were pure and holy".
Now it is amazing that if you do some quick math you'll see that it is quite plausible to see the "two-thirds" fit within the Zech. 13 prophecy and fulfilled in AD70.
But what happened to the other one-third?
Well, based on Jesus' clear warnings to His Jewish followers they would have been long gone. In fact Josephus records that between the attack of Vespasian and the seige under Titus, that many left the city.
Verse 16. Then let them which be in Judea flee into the mountains This counsel was remembered and wisely followed by the Christians afterwards. Eusebius and Epiphanius say, that at this juncture, after Cestius Gallus had raised the siege, and Vespasian was approaching with his army, all who believed in Christ left Jerusalem and fled to Pella, and other places beyond the river Jordan; and so they all marvellously escaped the general shipwreck of their country: not one of them perished. See on Matthew 24:13. (Adam Clarke, Commentary On Matthew 24)Jewish believers would have no reason to be in Jerusalem for the feast since they saw Christ as the True Passover and fulfillment of all the levitical symbols and temple services. IOW, unlike the apostate Jews, the believeing Jews were not compelled to be in Jerusalem for religious reasons. The history fits with the prophecies so well that it is really unnecessary to invent futurist scenarios.When therefore the Roman army shall advance to besiege Jerusalem, then let them who are in Judea consult their own safety, and flee into the mountains. His counsel was wisely remembered, and put in practice, by the Christians afterwards. Josephus informs us, that when Cestius Gallus came with his army against Jerusalem, "many fled from the city, as if it would be taken presently :" and after his retreat, "many of the noble Jews departed out of the city, as out of a sinking ship :" and a few years afterwards, when Vespasian was drawing, his forces towards Jerusalem, a great multitude fled from Jericho by an opening into the mountainous country, for their security. It is probable that there were some Christians among these, but we learn more certainly from ecclesiastical historians, that at this is juncture all who believed in Christ left Jerusalem, and removed to Pella, and other places beyond the river Jordan: so that they all marvellously escaped the general shipwreck of their country, and we do not read any where that so much as one of them perished in the destruction of Jerusalem. Of such signal service was this caution of our Saviour to the believers. (Thomas Newton, The Prophecy of Matthew 24, Dissertation XIX)
Finally.
We are agreed, then, that "Israel" in any particular scripture is a matter of correct interpretation of context.
Also, no dispensationalist I know denies that the clear Lu 21 example is dealing with Jesus prophecy of the sack of Jerusalem and the Temple.
Obeying Jesus, Christians would have fled.
But Jesus did not end with the sack of Jerusalem. He went on and predicted a "time of the Gentiles." He said that there would some day be an "end" to the time of the Gentiles control over Jerusalem. (Suggesting the Jewish retaking of Jerusalem.) He also said that in that era there would be signs in the earth and sky, that men's hearts would fail them for fear. That the sea would "roar." Finally he said that He would return. According to Preterists Jesus has already returned. They are wrong because, obviously, He has not. They are wrong or Jesus is wrong, because HE said He wouldn't return until after the time of the Gentiles in Jerusalem is finished. All prophecy couldn't have been fulfilled by 70 AD with the sack of Jerusalem. Jerusalem was just beginning to be under control of the Gentiles. That has lasted for some 20 centuries since, so the "time of the Gentiles in Jerusalem" was not over by 70 AD. And all those other signs contemporaneous with the "end of the time of Gentiles" have also not yet happened. Preterism is grossly in error.
... then we have to find a time in history before 70AD when 2/3rds of the Church was "slaughtered."
More silliness.
= = = =
ROTFLOL