The modern, secular world promotes a rather odd notion of freedom. Many people believe that freedom means doing whatever we want whenever we want regardless of what other people may think, sometimes with the condition that we don't hurt anyone else (usually without much thought to what actually hurts others and ourselves).
Zechariah's prayer provides a different idea of freedom...God's idea of freedom. God, says Zechariah, remembers His covenant, shows mercy, and frees His people from their enemies, but He doesn't free them so that they may simply do whatever they feel like. He frees them that they may serve Him and worship Him in holiness and righteousness.
So God frees us from something, namely, our enemies, whatever brings sin and death into our lives. But He also frees us for something, namely, to serve and worship Him in holiness and righteousness.
Freedom, then, in God's eyes is the ability to pursue Truth, Goodness, and Beauty. It is the power to worship without fear. It is the opportunity to discover what is right and to do it, to learn the truth and to embrace it, without the restraints of sin and error. It is the privilege to appreciate the beauty around and within us with wonder and joy. It is the delightful capacity to know and love God, to receive His plan for our lives with peace, to be set apart for Him as His beloved children, and to one day join Him in eternal bliss.
Now that is true freedom.