I wasn't aware that most Christians compare Acts with Zechariah. I'm not one of them though. I don't think Zechariah will be fulfilled until Jesus' second advent.
I think the scriptures are clear that the secret was not revealed until it was revealed to Paul, not at Jesus' first appearance.
Eph 3:3-5,
3 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,
4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)
5 Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
The Gospels are part of the "other ages" in which it was still kept secret by God. Those "other ages" technically ended on the day of Pentecost and not before. Wouldn't "now" mean when Paul wrote what he wrote? Looks like prior to that nobody knew about it.
1 Cor 2:7-8,
7 But we speak the wisdom of God in a mystery, [even] the hidden [wisdom], which God ordained before the world unto our glory:
8 Which none of the princes of this world knew: for had they known [it], they would not have crucified the Lord of glory.
If it was revealed when Jesus was here verse 8 would have no meaning. Jesus needed to die so God could raise him, which obviously ushered in a whole new age. The upshot of this mystery is Christ in you.
Col 1:27,
To whom God would make known what [is] the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:
There was nobody with Christ in them until the Day of Pentecost in Acts 2. That of course was 50 days after Jesus rose. The Apostles were the first to enjoy that privilege, followed by about 3,000 others after Peter's speech. If people could have had Christ in them before that day Jesus died for no reason.
When Jesus was alive there was one Jesus in one place. As bothersome as that was for the devil, he now has to deal with billions of Christs all over the place. No wonder he would not have killed Jesus had he known the mystery (secret). What a coup on God's part. The best the devil could do at that point was to prevent Christians learning about the secret. He's been fairly successful in that.
1 Cor 2:1-8,
1 And I, brethren, when I came to you, came not with excellency of speech or of wisdom, declaring unto you the testimony of God.
2 For I determined not to know any thing among you, save Jesus Christ, and him crucified.
3 And I was with you in weakness, and in fear, and in much trembling.
4 And my speech and my preaching [was] not with enticing words of man's wisdom, but in demonstration of the Spirit and of power:
5 That your faith should not stand in the wisdom of men, but in the power of God.
6 Howbeit we speak wisdom among them that are perfect: yet not the wisdom of this world, nor of the princes of this world, that come to nought:
7 But we speak the wisdom of God in a mystery, [even] the hidden [wisdom], which God ordained before the world unto our glory:
8 Which none of the princes of this world knew: for had they known [it], they would not have crucified the Lord of glory.
Paul was simply unable to reveal the fullness of that mystery to the Corinthians because they were carnal as evidenced by their infighting.
1Cor 3:1-4,
1 And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, [even] as unto babes in Christ.
2 I have fed you with milk, and not with meat: for hitherto ye were not able [to bear it], neither yet now are ye able.
3 For ye are yet carnal: for whereas [there is] among you envying, and strife, and divisions, are ye not carnal, and walk as men?
4 For while one saith, I am of Paul; and another, I [am] of Apollos; are ye not carnal?
Regarding my last dollar, I still think I can keep it, but it really doesn't matter since God meets my needs, not George Washington. :)