In[]:=
Exp1=Times[128,Power[alpha,3],Pi,Power[Plus[Power[Plus[m,Times[-1,M]],2],Times[-1,s],Times[-1,t]],Rational[-1,2]],Plus[Power[m,2],Power[M,2],Times[-1,s],Times[-1,t]],Power[Plus[Power[Plus[m,M],2],Times[-1,s],Times[-1,t]],Rational[-1,2]],Power[t,-2],Plus[Times[2,Power[Plus[Power[m,2],Power[M,2],Times[-1,s]],2]],Times[2,s,t],Power[t,2]],Plus[Log[Times[2,m,M]],Times[-1,Log[Plus[Times[-1,Power[m,2]],Times[-1,Power[M,2]],s,Times[Power[Plus[Power[Plus[m,Times[-1,M]],2],Times[-1,s],Times[-1,t]],Rational[1,2]],Power[Plus[Power[Plus[m,M],2],Times[-1,s],Times[-1,t]],Rational[1,2]]],t]]]]]
Out[]=
128π
3
alpha
(
2
m
+
2
M
-s-t)(2
2
(
2
m
+
2
M
-s)
+2st+
2
t
)log(2mM)-log-
2
m
+
2
(m-M)
-s-t
2
(m+M)
-s-t
-
2
M
+s+t
2
t
2
(m-M)
-s-t
2
(m+M)
-s-t

In[]:=
Exp2=Times[-128,Power[alpha,3],Pi,Plus[Power[m,2],Power[M,2],Times[-1,s],Times[-1,t]],Power[t,-2],Plus[Times[2,Power[Plus[Power[m,2],Power[M,2],Times[-1,s]],2]],Times[2,s,t],Power[t,2]],Power[Plus[Power[m,4],Power[Plus[Times[-1,Power[M,2]],s,t],2],Times[-2,Power[m,2],Plus[Power[M,2],s,t]]],Rational[-1,2]],Plus[Log[Times[2,m,M]],Times[-1,Log[Plus[Times[-1,Power[m,2]],Times[-1,Power[M,2]],s,t,Power[Plus[Power[m,4],Power[Plus[Times[-1,Power[M,2]],s,t],2],Times[-2,Power[m,2],Plus[Power[M,2],s,t]]],Rational[1,2]]]]]]]
Out[]=
-128π
3
alpha
(
2
m
+
2
M
-s-t)(2
2
(
2
m
+
2
M
-s)
+2st+
2
t
)log(2mM)-log
-2
2
m
(
2
M
+s+t)+
4
m
+
2
(-
2
M
+s+t)
-
2
m
-
2
M
+s+t
2
t
-2
2
m
(
2
M
+s+t)+
4
m
+
2
(-
2
M
+s+t)

In[]:=
Exp1+Exp2//FullSimplify
Out[]=
1
2
t
128π
3
alpha
(
2
m
+
2
M
-s-t)(2
2
(
2
m
+
2
M
-s)
+2st+
2
t
)
log(2mM)-log-
2
m
+
2
(m-M)
-s-t
2
(m+M)
-s-t
-
2
M
+s+t
2
(m-M)
-s-t
2
(m+M)
-s-t
+
log
-2
2
m
(
2
M
+s+t)+
4
m
+
2
(-
2
M
+s+t)
-
2
m
-
2
M
+s+t-log(2mM)
-2
2
m
(
2
M
+s+t)+
4
m
+
2
(-
2
M
+s+t)