96% Shroomish, but 13 Atk IV

I did Bite+Stone Edge (weather boosted by Partly Cloudy) with:
1 Breloom L32.5 (just to hit last breakpoint, ~70%IV)
3 Machamps around L36-37 (to hit last breakpoint)

The other guy had 5 high level Machamps, 1 Hary (around 35) and rejoined with an Aggron lol.

I dropped after the 3rd Machamp died, healed back Breloom (mistake) and the Champs and went back again.

We got it on first attempt.

Your Breloom is way better than mine but requires quite a hefty investment, mine was a wb caught.

So all you need really is power up your high Machop to L37. Your Hary is perfect already. You don't need Breloom, but that one will do easily. And quick relobbying. Also don't forget to relobby at a different time compared to your partner

You did forget to mention the level.
If the thing is low level, don't waste stardust on it.
If it's above 30, basically you'll just have to evolve and use it, so it's quite a gift (no cost!).
Then there is the moveset problem, but you could be lucky!
So the level IS the question.

Breloom is great in the first slot of a fighting team. Shroomish is fairly common here though, particularly this week with a grass event so I personally wouldn't invest in a hatched one. I've already got 3 lvl 33+ Brelooms with zero investment. His attack stat is higher than Machamps also, he's just noticeably glassier.

If you’re worried about “only” having 13atk then I don’t see the issue and just power him up because he could be good to use. Obviously glassy but does have higher attack. Like others said it comes down to level and since you seem to have a few others that are much higher level than I would start with them but if you have the dust and candy and like Breloom then I think that would be what you should do. It’s great to have a team of Machamps but I personally like doing gyms or raids without feeling like I need only the optimal counters in every situation. It’s more fun to use Pokemon you like imo

Since it's not above level 30, don't bother. Machamp is the only fighting type worth powering up from below 30, and even then good IV and moveset (to a lesser extent) are important. Catching a weather boosted shroomish or makuhita and evolving that is the better way to go. A high level wild catch can serve as a temporary place holder until you get a gem of a machamp worth powering up.

If you get lucky and catch a great weather boosted shroomish or makuhita you just saved yourself ~100k dust.