def Zlm(l, m, th, ph):
from sympy import simplify
if m > 0:
zz = C.NegativeOne()**m*(Ylm(l, m, th, ph) + Ylm_c(l, m, th, ph))/sqrt(2)
elif m == 0:
return Ylm(l, m, th, ph)
else:
zz = C.NegativeOne()**m*(Ylm(l, -m, th, ph) - Ylm_c(l, -m, th, ph))/(I*sqrt(2))
zz = zz.expand(complex=True)
zz = simplify(zz)
return zz
