Zac Brown’s Old Love Song is over. The country singer has separated from his second wife, Kelly Yazdi, after just four short months of marriage and has plans to divorce her, RadarOnline.comcan reveal. The pair secretly said “I do” on August 31 in Coweta County, Georgia, but the honeymoon is already done. Brown, 45, and Yazdi, 32, released a joint statement about their separation and the impending end to their short-lived marriage. “We are in the process of divorce. Our mutual respect for one another remains. We wish each other the best and will always appreciate our time together. As we naviga…