Chasing a Duckworth/Lewis target of 162 off 38 overs, Shafiq's mature innings and a solid knock by Mohammad Hafeez (49) steered Pakistan to an easy win with 23 balls to spare. They finished on 164-3.
Pakistan was never under pressure to score the runs and they chased down the total by collecting ones and twos and hitting the odd boundary.
The result meant the 1992 champions joined Australia, New Zealand and Sri Lanka from Group A in the knock out stages of the competition.
Earlier, pace duo Umar Gul and Abdul Razzaq rattled the Zimbabweans by reducing them to 13-3 inside six overs and they struggled to recover from that setback before rain intervened to mercifully halt their innings.
They amassed 151-7 after 39.4 overs but the victory target was adjusted according to the projected score the Africans would have reached had they been able to bat out their full quota of overs.
With the exception of Craig Ervine (52) and captain Elton Chigumbura (32 not out), the Zimbabwean batsmen struggled to come to terms with the stop-start nature of the contest due to three rain delays.
Following a delayed start, the cricketers first had to run for cover with Zimbabwe on 96 for five after 27.2 overs.
With 90 minutes of action lost, the match was first truncated to 43 overs a side before another deluge forced yet another adjustment. Ervine hit five fours during his stay at the crease while Chigumbura's hopes of celebrating his 25th birthday with a big score was scuppered by the rain gods.
Gul was the pick of the Pakistani bowlers with three for 36.
This is the second World Cup match to be affected by rain after Sri Lanka's showdown with Australia was washed out in Colombo earlier this month.
