The original Zouaves were native North African troops serving in the French Army in the 1830s. They wore distinctive uniforms. The uniforms usually consisted of a fez and turban, very baggy pants, a vest, a short jacket that was cut away from the top with only one button or clasp at the throat and a sash. They also wore leggings. The uniforms were usually brightly colored and had much trim and/or braid and many brass buttons on them.
These soldiers fought in North Africa for French interests. Later Zouaves fought in the Crimea and Italy in the 1850s. These troops were well trained and disciplined and were famous for great feats on the battlefield, and often mischief and rowdiness off the battlefield.
Prior to the US Civil War, "Zouave fever" spread to America. The colorful uniforms and fancy drill caught on with many city's militia units. This was particularly true after Col. Elmer Ellsworth took his Chicago Zouave Cadets on a tour of North America, challenging militia units to drill competition.
The 72nd Pennsylvania wore a modified Zouave uniform, with Chausseur pants and jackets with little fancy trim. Their trademark was their vest and leggings.
By the end of the Civil War most Zouave uniforms had disappeared due to the Army not wanting to replace them. There were however units that maintained the Zouave uniforms throughout the war, and actually were given Zouave uniforms to recognize the bravery of the unit.
Zouaves disappeared at the end of the Civil War in the US, except for veteran's groups. They continued on in the French Army until World War I when the ability to blend into the battlefield required more traditional green uniforms.
Further information about Zouaves can be found in the book: Zouaves, The First and the Bravest, by Michael J McAfee, Thomas Publications, Gettysburg, PA