Zimmerman in 1979 during the Belgian Championships improved the Belgian record in the 400 m hurdles with a time of 51.36 s. it was the first of four consecutive titles.Also that year he was sixth at the European Championships for juniors.
In 1982 took part in the European Championships Zimmerman for seniors. He was eliminated in the semifinals. Highlight for him was the year 1984. He recaptured at the Belgian Championships with his national record of 49,64 Rik Talwar and he competed at the Olympic Games in Los Angeles, where he reached the final with a time of 49,75. In it, he was seventh. In 1987 he captured his last Belgian title. He took that year also participated in the World Championships in Rome, where he played the series.
Zimmerman was affiliated with "Cercle Sportif Forestoise" (CSF, Frost) and Excelsior.
|400 m hurdles||1979, 1980, 1981, 1982, 1984, 1987|
|400 m hurdles||49,64 s||July 8, 1984||Brussels|
- 1979: 6th European Junior Championships in Bydgoszcz – 51,71 s
- 1979: AC- BK 51.36 s
- 1980: BK AC -51,27 s
- 1981: BK AC -50,59 s
- 1982: 51,06 BK AC -s
- 1982: 6th in ½ fin. European Championships in Athens – 50.83 s
- 1984: AC-49,64 BK s
- 1984: 7th OS in Los Angeles – 50,69 s
- 1986 EUROPEAN CHAMPIONSHIPS in Stuttgart in series: DNS
- 1987: 50,40 BK AC -s
- 1987: 6th in WORLD CUP series in Rome-50.70 s