Which one is correct?
This:
Everyone chose XYZ because it (and the ones from last year) is the most reliable.
or:
Everyone chose XYZ because it (and the ones from last year) are the most reliable.
Which one is correct?
This:
Everyone chose XYZ because it (and the ones from last year) is the most reliable.
or:
Everyone chose XYZ because it (and the ones from last year) are the most reliable.
The first sentence is correct.
Everyone chose XYZ because it (and the ones from last year) is the most reliable.
In the case of conflict between grammatical numbers in the sentence, the pronoun is matched according to the main sentence, and not the phrase inside the parenthesis.
*Note: When you put something in parenthesis, the sentence should have complete meaning and correct grammar even if you completely remove the parenthesis.