Correction: Bird does not agree with Zinsser's argument.

Agree to and agree with are phrasal verbs, which are verbs plus prepositions. Phrasal verbs change meaning depending on which preposition is added. Agree to means to agree in the sense of agree to a contract or requirement (Joe agreed to come early each day that month). Agree with means to share a common idea or opinion (Jack agreed with Sally about which restaurant was best).

Check the following resources for useful practice material: 1) Guide to Grammar and Writing, 2) Colleen Hildebrand's UCI Correction Symbols with hyperlinks.

For more about idioms and phrasal verbs, consult the LARC Electronic Writing Center Grammar Checklist.