The z axis is the 3rd dimension but your plot is 2D.
You yyaxis to assign an independent label to the right y-axis. Then link the two yaxes so that if properties of one change, the other axis will remain identical.
Demo:
% Create a demo uiaxes
app.UIAxes = uiaxes();
% Define right axis label
yyaxis(app.UIAxes, 'right')
ylabel(app.UIAxes, 'Right Side Label')
% Set axis colors to match the x axis color
set(app.UIAxes.YAxis, 'Color', app.UIAxes.XAxis.Color)
% Go back to the left y-axis and assign ylabel
yyaxis(app.UIAxes, 'left')
ylabel(app.UIAxes, 'Left Side Label')
% [DO ALL PLOTTING HERE]; Demo:
plot(app.UIAxes, randi(100,1,20), randi(50, 1,20), 'o')
% After plotting is done, link the y axes
% Link yaxis properties
app.UIAxes.UserData = linkprop(app.UIAxes.YAxis,...
{'Limits','LimitsMode','TickValues','TickLabelFormat','Scale',...
'Color','FontSize'}); %add more as needed
Result:
