hysterectomy doesn't get rid of endo. zoladex doesn't cure endo.
All it does it make you so damn miserable with other side effects while it stops your periods...but there are other ways to stop you periods besides a hysterectomy.
Mirena Coil- I found it excellent
MEA (Microwave endometrial ablation) sessions which cook the uterus wall to stop it from growing menstrual lining each month. Even if it doesn't stop periods entirely it can reduce them a lot for some ladies.
BC Pills. Norethisterone etc.
You can stop the zoladex right now and not have the next implant if it is making your quality of life a misery. It isn't curing endo. and taking it is voluntary.
No one is forcing you to carry on with it.
If you think you can manage another 7 weeks of it and haven't taken HRT add back hormones it might be worth speaking to your GP about that. HRT can lessen the impact of some of the side effects. Anti-depressants too can help you cope better.
Zoladex does give you depression.
If you do decide to stop, then expect the side effects to start wearing off in the 2-3 weeks after the last implant would have taken place if you had had it.
As for your periods they might return in a month, but on average it takes about 5 months for the ovaries to get working again, for some ladies it does take longer and all that time is without the side effects of the zoladex, so the quicker you come off it then quicker you will be feeling better for a while.