What is the peak time and half life of zanax xr and if given in the morning 8am would it sustain you til bedtime 10pm?

Good question. It is said to achieve effective concentration in 1-2 hours, and to sustain that for about 6 to 10 hours, with a half-life of 11 hours. But there is variation depending on food, and on the individual person. And it isn't clear if you need the full blood level later in the day for you to have the effect you need. So you need to empirically find out, working with your prescribing doctor.
Yes. The peak time is usually about 9 hours after its taken. It can be faster depending on whether you take it with a high fat meal. It could last til 10pm. The usual half life is 10-16 hours.