How can I use "Reduce" to solve equation with complicated form?

Here I used Reduce to solve that complicated equation in complexes but MMA didn’t give an answer after a few mins. I wonder whether there’re some functions could solve equations like that or not in MMA. Much appreciation if help!

equation=-1. (-4. + z^2) (2.56 - 4.64 z^2 + z^4) + (-0.5 + z)^2 (-4. + z^2) (2.56 - 4.64 z^2 + z^4) + 0.125 (-HeavisideTheta[1 - Norm[0.5 (-z - Sqrt[-4. + z^2])]] + HeavisideTheta[1 - Norm[0.5 (-z + Sqrt[-4. + z^2])]]) - 0.75 (-0.5 + z) (1. Sqrt[2.56 - 4.64 z^2 + z^4] (-HeavisideTheta[1 - Norm[0.5 (-z - Sqrt[-4. + z^2])]] + HeavisideTheta[1 - Norm[0.5 (-z + Sqrt[-4. + z^2])]]) + z Sqrt[-4. + z^2]Sign[-1 + Norm[0.595238 (-2.32 + z^2 + Sqrt[2.56 - 4.64 z^2 + z^4])]]);
Reduce[equation==0,z,Complexes]

(* Out: Reduce[equation==0,z,C] plus a warning message. *)

equation=-1. (-4. + z^2) (2.56 - 4.64 z^2 + z^4) + (-0.5 + z)^2 (-4. + z^2) (2.56 - 4.64 z^2 + z^4) + 0.125 (-HeavisideTheta[1 - Norm[0.5 (-z - Sqrt[-4. + z^2])]] + HeavisideTheta[1 - Norm[0.5 (-z + Sqrt[-4. + z^2])]]) - 0.75 (-0.5 + z) (1. Sqrt[2.56 - 4.64 z^2 + z^4] (-HeavisideTheta[1 - Norm[0.5 (-z - Sqrt[-4. + z^2])]] + HeavisideTheta[1 - Norm[0.5 (-z + Sqrt[-4. + z^2])]]) + z Sqrt[-4. + z^2]Sign[-1 + Norm[0.595238 (-2.32 + z^2 + Sqrt[2.56 - 4.64 z^2 + z^4])]]);
FindInstance[equation == 0, z, Complexes]