The tourists were reduced to 76 for three but Masakadza and Ervine came together to put on in excess of 100 runs, with the former making 60 and the latter 80 as the home side were given plenty to think about.
Zimbabwe finished on 273 for eight and it was only the brilliant bowling of Dwayne Bravo, who finished with six for 43, that gave West Indies a fighting chance.
With opener Vusi Sibanda also raising his bat for a tidy 51, it was a much more accomplished performance from Zimbabwe than the one they produced in their 156-run submission two days ago, although it had looked as though West Indies would dictate play early on.
Despite Sibanda going well, Chamu Chibhabha was castled by Sunil Narine for 11 and, when Sibanda and Brendan Taylor were cleaned up in the space of three Bravo balls, trouble looked on the cards.
But Masakadza and Ervine steadied the innings, with the former eventually sent back to the pavilion when he took on Bravo one too many times and found the hands of Narine at third man.
Malcolm Waller clubbed two sixes in a breezy 26 that was ended by Kemar Roach and when Ervine was cleaned up by Bravo, resistence appeared to be over.
But a cheery 15 from Regis Chakabva and 12 from Prosper Utseya added some bonus runs, with Bravo then having the last word as he got rid of the former and Kyle Jarvis.