Zinc as mentioned could help. However, be aware of the toxicity limit of Zinc. Depending on where you get your info and the size of the person, anywhere from 50mg to 100mg per day is the limit. That includes all sources of intake, so don't take a pill that is at the limit, because you've also gotten some from food. Staying below 50mg would be fine.
Folic acid and Flax Seed (Omega 3) are often recommended for sperm production. If you're researching herbs you'll find many that can increase sperm as well. Such as Epimedium (horny goat weed. Not to be taken consistently for long periods of time), Male Silk Moth drops, Cuscuta, Polygonum, Tribulus Terrestris, etc.
Of course you can find combo supplements already made for this purpose as well. Some of those might help with erection problems as well, as they may increase testosterone, overall sexual health, etc.
As for the shooting strength, that's usually the result of pelvic muscle strength which can be accomplished through Kegel or PC exercises. They can improve erections, strengthen orgasm, and ejaculate strength. However, be careful as to not cause PE as using these muscles can also trigger ejaculation.
Sometimes it's just a matter of when the muscles are tightened and relaxed, and other times the state of arousal.
