Zeferino, a three-time Olympian, first competed for Cape Verde in a meet in Maia, Portugal setting a national record in the 3000 metres steeplechase which still stands today.

Six months later at the 1999 Championships, he finished the marathon slightly slower in 2:26:03 which placed him in 39th position.

Zeferino's final race was the marathon at the 2004 Athens Games where aged 38, he finished in 78th with a time of 2:36:22.

Zeferino also completed in the 1998, 1999 and the 2003 IAAF World Half Marathon Championships finishing 117th, 91st and 70th respectively and also completed in the 1999 and the 2000 IAAF World Cross Country Championships – Senior men's race where he finished in 141st and 145th place respectively.

After retiring from active competition Zeferino became an English teacher in Barcelos, Portugal where he resides.