Equity Commonwealth stands to net a tidy profit from the sale of Triangle Plaza. : Sam Zell's office company is getting out of the Chicago market with a bang.The billionaire investor's Equity Commonwealth is finalizing a deal to sell the Triangle Plaza office complex—its last remaining Chicago-area office property—for around $143 million to Honolulu-based Shidler Group, according to sources familiar with the deal. That would be 49 percent more than the $96 million Equity Commonwealth paid in 2010 for the 14-story buildings at 8750 and 8770 W. Bryn Mawr Ave., Cook County property records show.