the muzzle seems fine considering it's a cartoon-esque drawing, but if you wanted to study shapes like this, you could always refer to things like the duck hunt dog. cheers!

I think the muzzle may need a more slightly angular shape to show the perspective and justify its size in relation to the rest of the face :) Doing some quick anatomy studies by sketching real animals in similar poses could help you to nail the proportions and then toonify/stylise them the way you like much easier
Love your sketchy style lineart and the cute tongue blep <3 keep it up