But assuming ZB had good load factors as was often said, then surely there isn't over capacity. Could be a case of high LF's but low yields, but doesn't mean another airline couldn't make it work out for them.
I am guessing that it's high LF and low yields which are the problem.
Given the "catchment areas" (and on another thread this whole question has been discussed) it is surprising that EMA has more available seats, and carries more PAX to some of the major Med. destinations than BHX. The problem is that if you lay all these seats on, then it's better they are sold than not, as any revenue is always better than none. If "the price is right", many passengers will "come on down" to the airport where the best prices are available.
Now that Monarch has blinked (or woken up and smelt the coffee) I therefore believe the seat availability will go down, and the revenue up, which will be of considerable benefit of both FR and LS in particular.