Question: plotting a volume corresponding to the given inequalities

I have four spindle tori governed by the following equations:

f1=x^4+2*x^2*y^2+2*x^2*z^2+y^4+2*y^2*z^2+z^4-2*x^3-2*x*y^2-2*x*z^2-(79/25)*x^2-(104/25)*y^2-(8/5)*z^2+(104/25)*x

f2=x^4+2*x^2*y^2+2*x^2*z^2+y^4+2*y^2*z^2+z^4-2*x^2*y-2*y^3-2*y*z^2-(104/25)*x^2-(79/25)*y^2-(8/5)*z^2+(104/25)*y

f3=x^4+2*x^2*y^2+2*x^2*z^2+y^4+2*y^2*z^2+z^4+2*x^3+2*x*y^2+2*x*z^2-(79/25)*x^2-(104/25)*y^2-(8/5)*z^2-(104/25)*x

f4=x^4+2*x^2*y^2+2*x^2*z^2+y^4+2*y^2*z^2+z^4+2*x^2*y+2*y^3+2*y*z^2-(104/25)*x^2-(79/25)*y^2-(8/5)*z^2-(104/25)*y

I could plot the surfaces using implicitplot3d and I can imagine the volume common to these surfaces but I could not visualize it. So, am looking for a way to plot the volume covered by the surfaces such that f1<0, f2<0, f3<0 and f4<0. I know that it's easy in case of a 2D filled plot but is there any way this could be done for the 3D case? Any mathematical advice as to how to characterize or calculate this volume would also be great.

 

 

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