According to Bryke, Zaheer, in addition to being very spiritual, was a master martial artist before acquiring airbending. He made a career in professional fighting and may have even done some illegal jobs that required his skills, which explains why we was such a danger to the world, even as a non-bender. When he woke up in his cell and saw that he got airbending, he had practiced in secret before using his new skills to break himself and his friends out of jail.
As a martial artist, any weapon given to you becomes an extension of your body. The idea of Zaheer getting so good at airbending in such a short amount of time is equivalent to a real life master martial artist who can be given any weapon (broom, sword, stapler, etc.), and know exactly how to use it as an extension of their body.
“Jinora breaks her grandfather’s record for being the youngest airbending master, receiving her tattoos at age eleven, whereas Aang received his when he was twelve. She is also the first female airbending master in 171 years.”—Avatar Wiki (via ohchsinad)