Aramis Ramirez (3-for-4, two RBI) and Hart went back-to-back during a four-run second inning and Hart added a three-run blast in the next frame for Milwaukee, which pounded out 15 hits in the victory.
Norichika Aoki contributed three hits, including a two-run single, as Milwaukee evened its three-game series.
Estrada (5-7) struck out 11 in a dominating performance, scattering four hits while issuing a single walk. The right-hander exited with a 9-0 lead.
Houston struck for five runs in the ninth against Brewers mop-up man Livan Hernandez as Fernando Martinez, Brian Bogusevic and Tyler Greene all launched long balls.
Astros starter Dallas Keuchel (3-8) was rocked for seven runs on eight hits in a 2 1/3-inning outing.