I have to admit I have never flown there, nor would I have the need for customs/immigration. I did cite from the AIP though:
EHMZ AD 2.3 OPERATIONAL HOURS
1 AD operatorDaily: 0800-1900 (0700-1800).
Outside OPR HR BTN SR-SS by arrangement before 1800 (1700).
2 Customs and immigrationCustoms: SR-SS 1 HR PN
1).
Immigration: NA.