@Carl Love 

I ran your code: and it gave me the necessary hint. 

new worksheet: ran :

l1:=[1,2,3,4]; l2:=[5,3,1,0];

with(m);

l1*l1;  -> zip not found;

zip didn"t work either

new worksheet, ran:

l1:=[1,2,3,4]; l2:=[5,3,1,0];

zip(:-`+`l1, l2)  -> [6,5,4,4]

with(m);

l1*l1; -> 11   ; everything was fine

While I was wondering, what different setup I had, I found that my library setup caused the error. I had the two lines in my maple.ini:

libname := libname, "E:\\SkyDrive\\Schule\\Mathematik\\CAS\\Maple\\Lib";
savelibname := "E:\\SkyDrive\\Schule\\Mathematik\\CAS\\Maple\\Lib";

because I wanted my own libraries to be stored here.

After I deleted maple.ini everything worked.

Unfortunately now I don't see the package m.m anywhere, I suspected it in ...\Maple\lib, but it wasn't there.  where did it go? how can I delete it?

More importantly: how do I store my libs in the place I want them? - Well maybe, that's another Task,

Thanks a lot for your help,

B.

@Carl Love 

nop, did'nt work either, returned

I'm pretty sure, the i is local by default, didn't know the global ref to :-* though.

Very curious, that you can't reproduce the problem. I'm running Maple 17 32 Bit on Windows 7 Pro 64 Bit

Thanks for trying to help me.

here's my whole Example with output:

m:= module() option package; export `*`;
    `*`:= proc( a::list, b::list) option overload;
        local i;
         return add(i, i  in zip(:-`*`, a, b));
    end proc;    
end module;
l1:=[1,2,3,4];
l2:=[4,1,0,5];
with(m);
l1*l2;

OUTPUT:

m := module () export `*`; option package; end module
l1 := [1, 2, 3, 4]
l2 := [4, 1, 0, 5]
[`*`]
`*`+[5, 3, 3, 9]

---- end ---

thanks for your help again