Veteran wing Khris Middleton is returning to the Washington Wizards, agreeing to a three-year, $17.6 million contract as part of a six-team trade that will include several other agreed-upon transactions, according to a team source who spoke on condition of anonymity because the deal has not been completed.The last two seasons of Middleton’s deal will be partially guaranteed, the source said. Sign-and-trade arrangements must be for three seasons, but not all three seasons need to be guaranteed.The Wizards will acquire Middleton via sign-and-trade as part of a deal involving the Mavericks, Memphis Grizzlies, Milwaukee Bucks, Detroit Pistons and LA Clippers. The large deal will fold in several previously reported moves for cap purposes, including the Bucks’ acquisition of Caris LeVert from Detroit earlier Tuesday.As part of the trade, the Wizards will send guard D’Angelo Russell and two future second-round picks to the Grizzlies while receiving a future second-round pick from Dallas. The Wizards will give up a 2029 Lakers second-round pick and the Wizards’ own 2033 second-round pick to the Grizzlies, according to a league source who spoke on condition of anonymity because the deal has not been completed. The Wizards will receive a 2033 second-round pick from the Mavericks.