Gumbie fell to McCarthy one run shy of a half-century after lunch and Dion Myers was next to go for nine.
The runs which came so easily in the morning dried up and the pressure told as the wickets tumbled.
Craig Young removed skipper Craig Ervine (five) before Curtis Campher claimed the big wicket of Masvaure.
Sean Williams added 35 but that was the last score in double figures and he was the first of McBrine’s three wickets.
The spinner went on to take two wickets in two balls and there was only token resistance from the tail as Zimbabwe posted a disappointing total.
Ireland ended the day on a high and they will be eager to put early runs on the board when play resumes.
“It was a very good end to the day – I thought they played really well in the first session,” said McBrine.
“It shows the character we have in the squad the way we fought back. The way Barry bowled and Craig bowled in the afternoon session and how we finished it off at the end – it was very good.”