I don't think comparing these two tragedies is appropriate.
The Holocaust was the systematic, bureaucratic, state-sponsored persecution and murder of six million Jews by the Nazi regime and its collaborators. "Holocaust" is a word of Greek origin meaning "sacrifice by fire." The Nazis, who came to power in Germany in January 1933, believed that Germans were "racially superior" and that the Jews, deemed "inferior," were an alien threat to the so-called German racial community. During the Holocaust 6 million innocent Jewish people were murdered, out of 11 million innocent people that were murdered in total. The Holocaust took place on a span of 6 years.
On September 11, 2001, 19 militants associated with the Islamic extremist group al-Qaeda hijacked four airliners and carried out suicide attacks against targets in the United States. Two of the planes were flown into the towers of the World Trade Center in New York City, a third plane hit the Pentagon just outside Washington, D.C., and the fourth plane crashed in a field in Pennsylvania. Often referred to as 9/11, the attacks resulted in extensive death and destruction, triggering major U.S. initiatives to combat terrorism and defining the presidency of George W. Bush. Over 3,000 people were killed during the attacks in New York City and Washington, D.C., including more than 400 police officers and firefighters.
Both events were tragic and had catastrophic consequences.
9/11 was a day of terror that changed the face of the world.
The Holocaust spanned over 6 years and cannot and should not be compared to anything.