Museo de la Toma de Zacatecas, on Cerro de la Bufa, focuses on the 1914 battle that made the city a turning point in the Mexican Revolution. The displays are modest, but the location gives them force: you are standing on the ground that mattered.
Combine it with the viewpoint and monuments on the hill. Even if your Spanish is limited, the maps and photographs help explain why Zacatecas was so fiercely contested.