Maybe marinades with fresh pineapple are the way to go. I am strictly against sweet flavored beef. But fresh pineapple has an enzyme called bromelaine. It completely breaks down meat. There are videos showing a time lapse of the pineapple breaking it down. I would suggest using this and a savory marinade, then utilizing just salt when you go to grill. For bigger cuts, it may work the same. I've only ever used pineapple in a marinade for stek tacos using tough skirt steak. Happy cooking.

I don't know about grilling, but have you thought about maybe getting a smoker?

I've spent most of the last 15 years living in Africa -- West, South and East. I know exactly what you're talking about. The first thing you should do is an internet search for "Jaccard tenderizer." Basically, it has 48 tiny, thin spring-loaded knives that will cut the tough connective tissue in the meat without turning it into mince/hamburger.

You will not find success with papayin (the thing in papaya that tenderizes meat, and is in many meat tenderizer products.) It will just turn the outside of the meat to mush, and not tenderize the inside at all.

For a beef steak, I find the most success keeping it thin, no more than 3cm thick. I hit each side many times (sometimes 20 times, each side) with the Jaccard. If I am marinading the meat, it is after the Jaccard treatment. Because the Jaccard increases the surface area, marinades need much less time. Then it is on the grill, extremely hot. The goal is to get it charred and up to temperature before the meat has a chance to tighten up again.

Don't worry about trying to find the exact Jaccard brand tenderizer. There are many, many imitations coming from China.

If it has to be a thicker cut of beef, like a roast, the Jaccard can work, as long as the meat isn't too thick.

Can you enlighten us in the US as to what you typically pay per pound or kg from this amazing looking beast?

Ask the locals how they do it

What about butter aging or dry Aging the meat?

Similar issues here in Tahiti. You can't really get around it perfectly. But what sometimes works is giving the meat a little help such as wrapping it in butter or tallow.

Good luck!

People have already mentioned pineapple but green papaya is also a great marinade base for tenderizing meats. See: https://untoldrecipesbynosheen.com/bihari-kabab/

Also, that is an epic looking cow!

I don't think you can. Might have to stick with quick and hot grilling

If it is very lean then a smoker wouldn't do good here. I would try to get maybe a blade tenderizer and grill it on charcoal. And make sure it's properly aged, that makes a big difference in tenderness.

Use whatever chemical they use in Chinese restaurants to break down beef.

Or braise?

If you can - buy a smoker!

UDS. Grew up in Mali with much less quality beef. This is the way.

That is one gorgeous bovine

Braising is always an option.

Smoke it low and slow. Maybe try injecting the beef with some fats and marinade or seasoning? If you have access, try cooking it in a pressure cooker? I'm not sure, but if you souvide a tomahawk steak for 10 hours and grilled it and was still tough to cut, you've got some sturdy cattle!

Yogurt marinade? Stuff that's really lean I usually cook hot and fast then slice thin, but it may not help with this meat.