HARARE (Reuters) - Lawmakers from Zimbabwe s main opposition party MDC will hold a meeting on Tuesday to decide whether to join their ruling party rivals to impeach 93-year-old President Robert Mugabe, the minority chief whip said. Although Mugabe s ZANU-PF has the required two-thirds  membership to remove Mugabe, participation by the opposition could give a boost to a process that was started by the military s intervention last week. 