I forgot to add,
I thought moslems were involved at some point, you’re saying two factions, not three?
That phase of the war was the Croatia's seizure of lands that it considered to be part of its territory that were in the possession of Serbs or Bosnian Serbs.
The Croatian army's targets were Serbs inhabiting those areas, not the Bosnian Muslims - the Bosnian Muslims did not object to Croats claiming the land as long as the Serbs did not get it.
Essentially the entire war in the Balkans was about various ethnic groups (Bosnian Muslims, Albanians, Croats and Serbs) trying to assert the largest possible physical boundaries for their homelands in a region where competing land claims and resettlements created a chaotic quilt of territories.
Because the Serbs overplayed their hand in the beginning, creating significant ill will in the international community, the Croats and Albanians were able to successfully assert their claims at the Serbs' expense.