Didn't Varna was lost because the crusader did not deploy Hussite wagon tactic and the king attack the Ottoman head on which lead to his death?All these forces working together against the Ottomans would be like the Varna crusade, nobody coordinated and as a result the Ottomans won. Also of note it that the Ottomans were a gunpowder empire (they used a lot of non-gunpowder weapons of course too), this was a significant threat to many of the mentioned powers (partly why the Swiss and Hussites stopped being as successful).
They also didn't have Swiss pike tactics or longbowman.
Considering that each of those 3 can win by themselves against greater numbers, I think even when uncoordinated they could still fare better than the forces at Varna. Of course, the whole fight depend on if the Ottoman have good artillery during the 15th century or not, I know they have it in the 16th century, but I don't know if their field artillery is as good in 15th century.
These 3 are mostly tactically defensive army, although the Swiss charge their enemy.
Their defeat are often from what I understand come from falling to feint retreat or breaking their formation.
English defeat due to breaking formation and charged from the flank:
Battle of Formigny - Wikipedia
Lithuanian defeat because they leave their Wagenburg to a feint retreat:
Battle of the Vorskla River - Wikipedia
Hussite defeat from feint retreat:
Battle of Lipany - Wikipedia
Swiss defeat from pikes and crossbow fire:
Battle of Arbedo - Wikipedia
However here the English can counter Ottoman archer and cavalry attack, the Swiss can protect against sudden cavalry attack when charging and the Hussites provide a good tactic if the 3 fall back to defensive positions. I doubt the Ottoman infantry could stand against the Swiss and dismounted English man at arms.
The artillery could be charged by both the Swiss and the English on foot or countered by Swiss or Hussite artillery.