One way to vary the syntax of the text is to combine sentences since, in this way, your structures will be longer and more complex to follow. This could be done by means of links such as: however, in addition, therefore, etc. When using these words, you create semantic relations between the syntactic structures and make the reading process more difficult because, as I've I said, sentences become longer and therefore the reader has to keep more information in mind to follow the train of thought.
You could also vary the syntax by adding phrases or clauses. This option is similar to the previous one since it also refers to the complexity of the syntactic structures of the text.
The state of being parallel or corresponding in some way
Louis' win over Schmeling didn't end racial segregation in America, but it helped pave the way for future generations of civil rights activists. The victory made it easier for Jackie Robinson to break Major League Baseball's color barrier. "If there had not been a Joe Louis
