I´m having trouble in GC Nuke(Tao) vs Demo(Juhziz). Can anyone help?

Juhziz is the hardest General Challenge, because of the small resource pile, no good defensive position, early fast attack waves and SCUD storm timer is glitched.

What specifically is the problem? Are you being completely owned? Or can you hold your ground by make no advances?
How are you managing your base currently?

The main problem are Marauder tanks and Topol Ms, because he attacks very fast and It´s too difficult to place a good defence against everything.

I normally use three dozers and use one to build gattling cannons but because of only one target point at a time they cannot stand against Topol M´s missiles. In few words I have problems with the defense.

Use a lot of nuclear battlemasters instead of building defences. In Shockwave, the best defence is a good offence. Since your tanks are generally faster they will be able to take out the topols relatively easily, the extra little bit of speed they have helps against bikes and also when kiting enemy tanks/marauders. Just be sure to use them in a spread out group so that they don't all get popped by a demo trap.

Thanks a lot, Alias!!!! I beated him up combining your strategy and mine. It was a nuclear BOOM in his two bases.

Glad to be of assistance.