The Browser View add-on adds the option to render HTML responses like a browser.
It can be selected via the Response tab toolbar.
JavaFX is required to use this add-on, it can be obtained, for example, from Gluon HQ.
Once obtained ZAP needs to be configured to use JavaFX, which can be done with the following JVM arguments replacing with the appropriate path to the JavaFX’s lib directory:
--module-path /path/to/javafx/lib/ --add-modules javafx.swing,javafx.web
If ZAP is launched with the default startup scripts the JVM arguments can be specified through the JVM options panel.