Veteran middle-order batter Sean Williams was unbeaten on 145 as Zimbabwe posted 363 for four against Afghanistan on the first day of the first Test in Bulawayo on Thursday.The 38-year-old needs seven more runs to overtake his Test career best - an unbeaten 151 in a loss to Afghanistan in Abu Dhabi three years ago.Making his 16th Test appearance, Williams came in at No 4 after a 68 from debutant opener Ben Curran had lifted the home team to 92-2 at Queens Sports Club in Bulawayo. Playing in the southwestern city where he was born, Williams added 78 runs with Takudzwanashe Kaitano (46) for the third wicket and 50 with Dion Myers (27) for the fourth.He then partnered captain Craig Ervine (56 not out) in a 143-run stand as the Zimbabwe batters finally came good after a string of low white-ball totals in recent series losses to Pakistan and Afghanistan.Left-hander Williams, who made his Test debut against the West Indies in 2013, struck three sixes and nine fours off 161 deliveries for his fifth century. Ervine faced 94 balls and hit six fours in the first Boxing Day Test hosted by Zimbabwe since a rain-affected draw with England in Harare 28 years ago. Curran, a son of deceased former Zimbabwe coach Kevin Curran and brother of England internationals Tom and Sam, included 11 fours in his 74-ball knock.Opener Joylord Gumbie was the only Zimbabwean who failed to reach double figures. He was out for nine when caught by wicketkeeper Afsar Zazai off a delivery from medium pacer Naveed Zadran.Teenage off spinner Allah Ghazanfar (2-83) was the most successful of the Afghan bowlers, taking the wickets of Curran and Myers.But the tourists’ attack was generally unimpressive. Too many deliveries were loose, they struggled with line and length, and were not helped by some sloppy fielding.Both teams are seeking a first Test victory since defeating each other in the United Arab Emirates three years ago.Brief scores (First test, Day 1)Zimbabwe 363-4 in 85 overs (Sean Williams 145 not out, Ben Curran 68, Craig Ervine 56 not out, Takudzwanashe Kaitano 46; Allah Ghazanfar 2-83) v AfghanistanToss: Zimbabwe