"[4][5] Against one of his most skilled early opponents, Zivic defeated Charley Burley, fellow Pittsburgh boxer, for the only time on March 21, 1938, in their hometown.

Zivic lost to Billy Conn, 1939 world light heavyweight champion, on December 28, 1936 before 5,163 in a ten-round split decision at Duquesne Garden in Pittsburgh.

The bout included no knockdowns but in the fourth and fifth rounds, Zivic caught Conn on the ropes and belted him about head and body til it appeared a knockout was a possible outcome.

From the sixth to the tenth, Conn fought more from a distance and in the eighth and ninth boxed brilliantly, using feints and footwork and his long, solid left.

[10] Zivic defeated Johnny Jadick, former junior welterweight champion, on February 11, 1937 in a six-round knockout at Duquesne Garden in Pittsburgh.

[12] He notably defeated Sammy Angott, reigning NBA lightweight champion, in a non-title bout on August 29, 1940, in a ten-round unanimous decision at Forbes Field in Pittsburgh.

[5] In the most significant win of his career, Zivic upset Henry "Hammering Hank" Armstrong on October 4, 1940 in a fifteen-round decision before 12,081 at Madison Square Garden, taking the world welterweight title despite being a 4-1 underdog.

Zivic mounted a slow effective attack, but held no wide margin, as the referee and both judges awarded him eight of the fifteen rounds in the close bout.

Zivic claimed Armstrong started out fighting that way, noting, "Henry's givin' me the elbows and the shoulders and the top of the head, and I can give that stuff back pretty good, but I don't dare to or maybe they'll throw me out of the ring.

[16] In his most memorable victory, he won the world welterweight title rematch with Hank Armstrong in a twelfth-round technical knockout, at Madison Square Garden, on January 17, 1941.

As the bout wore on, Armstrong tired badly, and was continuously the victim of Zivic's short uppercuts, which snapped back his head.

Armstrong caught Zivic in a corner and battered him with short jarring blows and then landed a right to the face, but it was a last valiant effort.

[17][8][18] Zivic lost his world welterweight title in a fifteen-round decision against Red Cochran before 10,000 fans on July 29, 1941 at Rupert Stadium in Newark, NJ.

[20] Immediately after his loss of the title, on September 15, 1941, Zivic achieved a fifth-round knockout of Milt Aaron in the feature match at Pittsburgh's Forbes Field, before an appreciative hometown audience of 24,972 fans.

[23] He lost to the great Sugar Ray Robinson, a future Hall of Famer, on January 16, 1942 in a tenth-round technical knockout before 15,745 fans at Madison Square Garden.

[24] Zivic defeated Italian boxer "Izzy" Anthony Jannazzo on March 9, 1942, leaving Janazzo unable to return to the ring for the fifth round at Duquesne Gardens in Pittsburgh.

[25] A skilled middleweight, Jannazzo had contended for the world welterweight title against Barney Ross in November 1936 at Madison Square Garden.

On April 13, 1942, Zivic defeated Jewish Canadian boxer Maxie Berger, former holder of the Montreal Athletic Commission's Junior World Welterweight Title, in a ten-round points decision at Duquesne Gardens in Pittsburgh.

[26] In the fourth, Berger was hit by a low right from Zivic, and changed to more defensive tactics afterward, which reduced the slight points advantage he may have held in the first three rounds.

[8] Zivic lost to reigning world lightweight champion and future Hall of Fame boxer, Beau Jack in a non-title bout on March 5, 1943 in a unanimous but close twelve-round decision in Madison Square Garden before a crowd of 8,813.

If not for the foul call against Zivic in the eighth, the AP scoring would have been a draw, though the official ring judges considered Jack the victor by a slightly larger margin.

Zivic lost in two other meetings, one in January 1944, despite LaMotta losing two rounds from low blows, and one in November 1943 in a relatively close bout in Madison Square Garden.

Zivic lost to reigning NYSAC world lightweight champion Bob Montgomery on August 23, 1943 in a non-title, ten round unanimous decision at Shibe Park in Philadelphia.

Bell, a quality opponent who would challenge Robinson for the world welterweight title in 1946, made his thirty-eighth consecutive win with the victory.

[35] While still in the Army, Zivic defeated Billy Arnold on January 5, 1945, in a convincing eight round mixed decision at Madison Square Garden before an impressive house of 16,923.

[36] He never challenged for a world title after 1941, but from 1941 to 1946, he fought the great boxers Sugar Ray Robinson, Beau Jack, Tommy Bell, Billy Arnold, Jake LaMotta, and Freddie Archer.

"[37] Zivic served in the Army Air Corps during the end of WWII, being stationed for a time at San Antonio's Normoyle Field, where he continued his boxing schedule in Texas and the Southwest.

[5] He died after a long battle with Alzheimer's disease in 1984 after a three-year stay at Veteran's Hospital in Aspinwall, Pennsylvania, and was buried in Pittsburgh's St. Nicholas Cemetery.