Shower drain problem

[Diiorioj]

How should I Run the pipe from the drain I'm installing to the stub ? The top of the diagananal pipe is at the bottom of the cement and the stub can not be cut anymore because of fittings on it
See attached pics

 

[SHR]

You can not tie a shower drain in to the stub you show. Too small of pipe. You need 2" pipe and you have to remove the old tub drain p-trap. A lot more concrete removal is in your future if you really want to put a ceramic shower base in place of your tub.