动物园时间序列-扩展x轴在图

I created a time-series with zoo (following suggestions in another question that ts() is not good for daily time-series). I would like to extend the x-axis beyond the dates from my zoo object (in order to overlay a second time-series - neither "add=T" nor points() seem to work for zoo plots). I need to overlay (par(new=T)) the second time-series because the two have different scales. However, if I try to adjust xlim, it plots the axes, but not the actual data.I created a time-series with zoo (following sug