1. Questions: What would be the difference between a Jew and non-Jew together tying tzitzis and them together shechting an animal?
A. The case by shechting is where they are both holding onto the knife when slaughtering where the Shulchan Aruch Yoreh Deah 2:11 says it is no good.
B. You need an action of a kosher shechita done by a Jew but it does not transform the animal in any way but by tzitzis the four cornered garment is transformed into a tzitzis garment and the action required to be done by a Jew is just the means to transform it into a kosher tzitzis garment.
C. Why then would it be alright if a non-Jew made the tzitzis with the Jew even if it would not work by shechting the animal?
Answer: Since what is required by shechting is a kosher action then the whole action must be done only by a Jew according to the Shulchan Aruch. But by tzitzis you just need a garment of tzitzis made by a Jew and it was made by a Jew a non-Jew was just involved as well.