Cmd+0 is already taken for hiding the navigation sidebar.

src/plugins/help/helpplugin.cpp

@@ -243,7 +243,9 @@ bool HelpPlugin::initialize(const QStringList &arguments, QString *error)
         action = new QAction(tr("Reset Font Size"), this);
         cmd = am->registerAction(action, TextEditor::Constants::RESET_FONT_SIZE,
             modecontext);
+#ifndef Q_WS_MAC
         cmd->setDefaultKeySequence(QKeySequence(tr("Ctrl+0")));
+#endif
         connect(action, SIGNAL(triggered()), m_centralWidget, SLOT(resetZoom()));
         advancedMenu->addAction(cmd, Core::Constants::G_EDIT_FONT);
     }

src/plugins/texteditor/texteditoractionhandler.cpp

@@ -229,7 +229,9 @@ void TextEditorActionHandler::createActions()
 
     m_resetFontSizeAction = new QAction(tr("Reset Font Size"), this);
     command = am->registerAction(m_resetFontSizeAction, Constants::RESET_FONT_SIZE, m_contextId);
+#ifndef Q_WS_MAC
     command->setDefaultKeySequence(QKeySequence(tr("Ctrl+0")));
+#endif
     connect(m_resetFontSizeAction, SIGNAL(triggered()), this, SLOT(resetFontSize()));
     advancedMenu->addAction(command, Core::Constants::G_EDIT_FONT);