Question: Factorizing nested radicals

# The question is: how to get S knowing E?  All the attemps below after S assigned (suggested by Claude) fail factoring E.  

restart;

interface(showassumed = 0): 
assume(a>=0, b>=0, c>=0);
assume(x::real, y::real,z::real);

S := sqrt(x^2+(a+sqrt(y^2+(b+sqrt(z^2+c^2))^2))^2):
E := expand(S):
simplify(E,sqrt):
combine(E,sqrt):
simplify(combine(E, sqrt), sqrt):
evalindets(E, 'radical', f -> simplify(f, sqrt)):
simplify(radnormal(E), sqrt):

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