The past tense of weigh up the pros and cons of is weighed up the pros and cons of.

The third-person singular simple present indicative form of weigh up the pros and cons of is weighs up the pros and cons of.

The present participle of weigh up the pros and cons of is weighing up the pros and cons of.

The past participle of weigh up the pros and cons of is weighed up the pros and cons of.