The return flight has a 7-hour layover in Munich - that's on purpose. It's long enough to explore Munich itself, or just enjoy Munich Airport, which I've heard is a genuinely fun experience and one of the good airports.
Out and into Munich? The S-Bahn runs straight from the terminal - about 40 minutes to the city centre. Marienplatz and the Glockenspiel, the Viktualienmarkt food market, the Frauenkirche towers, the English Garden (one of the biggest city parks in the world, with river surfers on the Eisbach wave), and the pedestrian old-town shopping streets. Grab a last proper meal if we feel like it. This all works because Germany is in the same Schengen area as Croatia - just make sure your visa is multiple-entry and still valid on 17 July.
Or just stay in the airport. Munich is genuinely one of the best airports to be stuck in: a free Visitors Park with a runway viewing hill and a retired plane you can climb into, the MAC Forum's exhibitions, over 150 shops, free airport tours, and the world's only airport brewery with its own beer garden right in the middle of the terminal. Easy to spend the whole layover there without going through passport control.
I'm happy to make the bookings if it helps us land on the same flights - but if you find cheaper ones, that's totally fine too.