Things are a little clearer now. One thing about Fold3 is that you have to Browse the records of a soldier's unit or you will miss some of them, due I suppose to the way they are loaded if you pull him up as an individual soldier. At any rate, Morris resigned his commission as 2nd Lt of the 10th Louisiana Inf Jan/Feb 1862. He was still carried on their rolls as late as March 28, 1865 "In the trenches in front of Petersburg," but showing the date of his resignation. He was listed as born in Germany, a merchant by occupation, residence New Orleans. Most of his signatures on pay vouchers match, except for one, which might have been filled out by someone else.
As for the Louisiana Zouaves, he may have been conscripted into them in Virginia in 1864, on March 31. A return for Sept 1864 shows that he had been AWOL since June 29, 1864. His rank was given a private. No further record, other than his vouchers for his detective work in 1863. All of those are filed with his Zouave records.
If he was in the Zouaves from March 31 to June 29, 1864, why did the conscription officers in Texas think he might have been there in April 1864? There is no record of his having a furlough, and the letter re his whereabouts states his employment for the Bureau of Conscription ended on Jan 25, 1864. The poster who suggested that he may have made some powerful enemies may be onto something.
One very odd thing is that Morris Greenwall booked passage on the steamer
Marion for New Orleans in September 1862. New Orleans was in Union hands, so I'm befuddled.

[edit] Since his brother Phil was sent to New orleans after being captured about this time, it's possible Morris decided to book passage there to look in on him. One bio says Phil was wounded at Yorktown.
The
Marion was a steamer that sailed regularly between New York and New Orleans, also stopping at Havana, and other island ports. She was even seized by South Carolina forces during the
Star of the West incident in Jan 1861. Since she could not be converted into a warship, the ship, which usually carried the mail, was returned to her owners after 24 hours of captivity. How Morris Greenwall was able to travel to New York from New Orleans and back during wartime when he was a Confederate officer can only be guessed at. He was only 23 when the war broke out, but it's possible he had learned a lot about how ships were boarded and off-loaded. He may have known how to pass himself off as a loyal US citizen, which he certainly did in Oct 1864 when he applied for a passport. He would only need that if he was planning to make landfall outside the US, possibly in Cuba or the Westies.