Can you telll me how long after taking zpack will it stay in your body?

A long time: Half life of Azithromycin is 50-72 hours, so there should be active drug left in your body for several days afterwards. That is one of the reasons the z-pack is so useful; treat for 5 days, but have closer to 7-10 of active coverage.

15 days: The half life or time for 1/2 of the drug to be eliminated is approximately 3 days for azithromycin(zithromax in z-pak). Significant antibacterial activity against many pathogens remains in tissues for at least 5 days after completing a 5 day course of the drug. Drugs generally stay in the body for 5 half lives after the last dose so for Azithromycin it will stay in your body for about 15 days.