Very quickly! A great way to answer your question yourself, would be to purchase an inexpensive home BP unit (i like omron), and simply monitor your BP every hour or two. You should see results within hours.
Fast and slower..... With each pill you take, it will be in your system (so you may notice lower blood pressure) within 20 minutes. To know the full impact of a med like Lisinopril on your blood pressure you should take it, as prescribed, for at least 2 weeks before making decisions about dose adjustments, etc.
5 days. Most meds take 5 half lives to take effect. Lisinopril is once a day so at least 5 days for full dose effect.
In a matter of days. In a matter of days.