One of my big dissapointmenst with RedBaron3d Was they left out the Zepplins mission. Has anybody done a mod that brings the Zeps and the Zep missions to Red Baron 3d?

no, unfortunately ..
I was given the Dynamix Zep model years ago and have messed around with it in MP, replacing it in another plane's slot .. there's some pics of it here
http://www.flybert.net/aerocraft.htm
There's even a "slot" in the game for it ..
There's a bunch of Rb3D modders getting back together for the first time in years ..
I'll propose the question of how we might add the Zep and create missions for it ..
Interestingly enough , the Zep Shed 3d model is in the game, and can be enabled quite easily .. an I just read, at the swwisa forum that there is a ground objects location file type assignable for a Zep base ..
the biggest problem is making the Zep aircraft slot work .. but I'm sure we'll be willing to give it some fresh thought again