He was one of the greatest hitters of his era: especially after becoming the fulltime Cubs 3B in 1911. He hit .372 one year, and some say he won the Triple Crown in 1912 (RBI wasn't yet an official stat, and there is a dispute about his final tally).

But as great Zimmermann was hit in the batter's box, he was a trouble maker in the clubhouse, and a terrible fielder. In 1908 he almost cost outfielder Jimmy Sheckard his eyesight by throwing a bottle of ammonia at his face. His teammates, led by manager Frank Chance, beat him to a bloody pulp for that.

In 1914 he got into a fistfight with his teammate Roger Bresnahan on the field after Bresnahan complained about his shoddy fielding (he had several games where he made four errors in the same game). Later that season, he got into a fight with three players on the Braves, including former teammate Johnny Evers. He left the field that day with a bloody nose.

The next season he fought another teammate George Peace (after another complaint about his bad fielding), and this time pitcher Hippo Vaughn had to step in and break up the fight. He got a bloody lip for his efforts. It got so bad that a fan sent him half of a one-hundred dollar bill and promised to send him the other half if he could go two weeks without getting ejected. He never collected.

Heinie was traded to the Giants in 1916, and made a boneheaded error in the World Series the following year that helped the White Sox win the championship. In 1919 he walked up to the mound during a game against the Cubs and told the pitcher that it "would be worth your while" not to pitch too well that day. The pitcher, Fred Toney, told his manager John McGraw, who immediately kicked Zimmermann off the team. He and his teammate Hal Chase, a fellow suspected game fixer, were banned from the sport forever.

After his playing days were over, Zimmermann went into business with mobster Dutch Schultz and ran a speakeasy for him in New York.