To end the ongoing feud between Prochek and Olbram in the Kingdom Come: Deliverance 2 side quest, "Battle of the Frogs and Mice," follow these steps for a peaceful resolution.
The "Battle of the Frogs and Mice" side quest becomes available after completing either the Mice or Frogs quests for Prochek or Olbram. Once you've finished one of these quests, you can initiate the new quest by speaking to Prochek in Tachov or Olbram in Zhelejov. After starting the quest, proceed to the designated pasture to begin.
While you can choose to side with either Prochek or Olbram, the optimal outcome involves stopping the feud entirely. To side with Prochek, talk to him in Tachov and say, "Let’s get those Zhelejovites!" To side with Olbram, speak with him in Zhelejov and say, "Let’s go and see those Tachovites!" However, siding with either will lead to a confrontation, and you'll only receive groschen as a reward.

For a more satisfying resolution, you can end the feud altogether. Before heading to the pasture, ask Prochek or Olbram if they want to end the feud. Then, travel to Troskowitz and speak with Baliff Thrush, choosing the dialogue option, "You’d finally have some peace." Successfully passing the dialogue check will allow you access to the scribe’s room to read the Troskowitz Chronicle. If persuasion fails, you can sneak in to read it, but make sure to save your game first.
Once in the scribe’s room, engage with the scribe and select the dialogue option, "Fecit, ordinem in regione ope clavi ferrei."

Next, go to the pasture and locate three oak trees lined up next to each other. Examine the middle tree to find a nail. Your options with the nail are:
The choice of where to place the nail is yours and does not significantly impact the outcome, so choose based on your preference or stay neutral. After deciding, speak with Baliff Thrush again, who will agree to end the feud. Then, bring Prochek or Olbram to the pasture to finalize the resolution.
Afterward, speak with Baliff Thrush to receive the "Master Studies I" book as a reward.
This approach ensures a peaceful end to the feud between Prochek and Olbram in Kingdom Come: Deliverance 2. For more tips and information on the game, visit The Escapist.