Question: Simplify RootOf() expression

Hi!

I have a question here. Is there any way to simplify a complicated number expressed in terms of RootOf() forms?

I got numbers like

c:=(3/128)*RootOf(3*_Z^4-20*_Z^3+50*_Z^2-20*_Z+3)^3-(5/32)*RootOf(3*_Z^4-20*_Z^3+50*_Z^2-20*_Z+3)^2+(1/64)*sqrt(4+6*sqrt(6))+(25/64)*RootOf(3*_Z^4-20*_Z^3+50*_Z^2-20*_Z+3)-(3/128)*RootOf(3+3*_Z^2+(-3*RootOf(3*_Z^4-20*_Z^3+50*_Z^2-20*_Z+3)^3+20*RootOf(3*_Z^4-20*_Z^3+50*_Z^2-20*_Z+3)^2-47*RootOf(3*_Z^4-20*_Z^3+50*_Z^2-20*_Z+3))*_Z)-5/64

I am quite sure this number is 0: 
evalf(c, 100) gives:
0.+1.*10^(-101)*I

However, I tried simplify(c) and convert( c, 'radical' ) and some other choices of simplify() function. None of them can output 0. Is there any maple functions that can help me to simplify this kind of expressions?

Thanks!

William