diff --git a/browser/base/content/browser-init.js b/browser/base/content/browser-init.js
index 9df41bb3c82919839ee1408aa4d177ea7ee40a56..e37c64fa2c2ea39762be4285a1a7055463ded537 100644
--- a/browser/base/content/browser-init.js
+++ b/browser/base/content/browser-init.js
@@ -152,13 +152,15 @@ var gBrowserInit = {
       // tell CUI to ignore this element when it builds the toolbar areas
       elem.setAttribute("skipintoolbarset", "true");
     }
+    ZenCustomizableUI.init(window);
     for (let area of CustomizableUI.areas) {
       let type = CustomizableUI.getAreaType(area);
-      if (type == CustomizableUI.TYPE_TOOLBAR) {
+      if (type == CustomizableUI.TYPE_TOOLBAR && !area.startsWith("zen-")) {
         let node = document.getElementById(area);
         CustomizableUI.registerToolbarNode(node);
       }
     }
+    ZenCustomizableUI.registerToolbarNodes(window);
     for (let elem of nonRemovables) {
       elem.setAttribute("removable", "false");
       elem.removeAttribute("skipintoolbarset");
@@ -253,6 +255,10 @@ var gBrowserInit = {
     gPrivateBrowsingUI.init();
     BrowserSearch.init();
     BrowserPageActions.init();
+
+Services.scriptloader.loadSubScript("chrome://browser/content/ZenStartup.mjs", window);
+Services.scriptloader.loadSubScript("chrome://browser/content/zenThemeModifier.js", window);
+
     if (gToolbarKeyNavEnabled) {
       ToolbarKeyboardNavigator.init();
     }