In 1856, aged 55, Zastrow married countess Ottilie von Rantzau, who was sixteen years his junior.

Promoted to colonel he commanded the 28th Infantry Regiment and afterwards the 19th brigade as a major general.

[1] During the Austro-Prussian War Heinrich von Zastrow commanded 11th Division part of Second Army.

[3] When the Franco-German War erupted in 1870 Zastrow was given command of VII Corps (part of Steinmetz's First Army), with which he distinguished himself at Spicheren, Gravelotte and the siege of Metz.

In the last phase of the war VII Corps was part of Manteuffel's Army of the South.