When you've seen God the Son you've seen God the Father.
(John 10:29-30 NIV) My Father, who has given them to me, is greater than all ; no one can snatch them out of my Father's hand. {30} I and the Father are one."
(John 14:6-11 NIV) Jesus answered, "I am the way and the truth and the life. No one comes to the Father except through me. {7} If you really knew me, you would know my Father as well. From now on, you do know him and have seen him." {8} Philip said, "Lord, show us the Father and that will be enough for us." {9} Jesus answered: "Don't you know me, Philip, even after I have been among you such a long time? Anyone who has seen me has seen the Father. How can you say, 'Show us the Father'? {10} Don't you believe that I am in the Father, and that the Father is in me? The words I say to you are not just my own. Rather, it is the Father, living in me, who is doing his work. {11} Believe me when I say that I am in the Father and the Father is in me; or at least believe on the evidence of the miracles themselves.
(Isaiah 9:6-7 NIV) For to us a child is born, to us a son is given, and the government will be on his shoulders. And he will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace. {7} Of the increase of his government and peace there will be no end. He will reign on David's throne and over his kingdom, establishing and upholding it with justice and righteousness from that time on and forever. The zeal of the LORD Almighty will accomplish this.
(Zechariah 12:9-10 NIV) On that day I will set out to destroy all the nations that attack Jerusalem. {10} "And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and supplication. They will look on me, the one they have pierced, and they will mourn for him as one mourns for an only child, and grieve bitterly for him as one grieves for a firstborn son.
When was God pierced? Wasn't it when his own people crucified him?
When we are one with the Father as Jesus was (which John 17 tells us that we are) when you see us, you see the Father. I discussed how further in this article: http://lothealing.com/coming-in-our-fathers-name-praying-in-jesuss-name/
Just because you have the "name" of something, doesn't mean you are something. We have the name of YHWH in Revelation, but it doesn't make us YHWH. And if you think that's referring to Jesus, then you have two everlasting Fathers. YHWH accomplished it by raising his son up as a messiah.
As for Zechariah, they pierced the son, not the Father. This video will help clear that mistranslation up.
As it is, it says they'll look on the one they pierced and mourn for someone else. You can easily tell there was a translation problem.
If you're interested in studying this out you can check out this website too: http://www.angelfire.com/space/thegospeltruth/trinity.html
I used to believe in the trinity until I found out how illogical it was and how many translation problems there were that led to people being confused about the issue. That website helped a lot.