Compare the following examples:
"She likes to cook, jog, and read."
"He likes to play baseball and to run."
All of the above examples are grammatically correct, even if they lack parallelism: "cooking", "jogging", and "to read" are all grammatically valid conclusions to "She likes", for instance. The first nonparallel example has a mix of gerunds and infinitives. To make it parallel, the sentence can be rewritten with all gerunds or all infinitives. The second example pairs a gerund with a regular noun. Parallelism can be achieved by converting both terms to gerunds or to infinitives. The final phrase of the third example does not include a definite location, such as "across the yard" or "over the fence"; rewriting to add one completes the sentence's parallelism.
Further information: Parallelism (rhetoric)
Parallelism is often used as a rhetorical device. Examples:
Gary Blake and Robert W. Bly, The Elements of Technical Writing, pg. 71. New York: Macmillan Publishers, 1993. ISBN 0020130856 /wiki/Gary_Blake ↩
For the point about processing, see Carlson, Katy. Parallelism and Prosody in the Processing of Ellipsis Sentences. Routledge, 2002, pp. 4–6. https://books.google.com/books?id=lIJ7quEJl8gC&pg=PA4 ↩
"Rhetorical Figures in Sound: Parallelism". American Rhetoric. Archived from the original on 15 January 2018. http://www.americanrhetoric.com/figures/parallelism.htm ↩
"Vice of Capitalism". International Churchill Society. Retrieved 15 January 2018. https://www.winstonchurchill.org/resources/quotes/vice-of-capitalism/ ↩