How long does it take for zithromax to cure chlamydia and does it also cure pelvic inflammatory disease?

Two weeks. Most providers recommend avoiding intercourse for two weeks after treatment followed by a rest to make sure the infection has resolved. Zithromax can be used as part of the treatment for PID along with other medications.
See below. It probably takes a few days for all the chlamydia to be killed by the zithromax. It would not be enough to treat pid, however. You would need to take antibiotics that cover gram positive and gram negative and anaerobic bacteria.