Upload & Sell: Off
Manu, as I mentioned Zeiss ZF.2 lenses will be available for a long while while some Leica-R (search for Mandler's designs) are harder to get, at least in a great shape. Newer Leica designs may be optically better, but that's where current Zeiss comes to play.
You already have few Leica-R lenses and the list is just about completed depending on tastes. Cron-R 35 can be yours for around $1200, and I can tell you it will be your lifetime lasting purchase, just like Cron-50.
Don't sell your Zeiss 2/35 - it's a great lens and you will lose too much $$$ selling it.
We picked up expensive hobby, you know, and for me it's still on pair with high end audio I actively support (I won't even mention my vinyl purchases!)
Christmas comes soon -get the 35 Cron-R on account of it!