do is

  1. All I can do is to call the police.
    1a. All I can do is call the police.
    1b. All I can do is calling the police.
  2. What we do is to pack the final products.
    2a. What we do is pack the final products.
    2b. What we do is packing the final products.
    Please correct the above sentences.
    Thanks.

1 and 2 contain an unnecessary ‘to’ which it is better to drop.
1b and 2b are completely incorrect.

1a and 2a are the best options.

Hi, Beeesneees

I usually see some sentences like : Waiting for you is the most stupid thing I’ve ever done.
Can I write :

Packing the final products is what we do.
Calling the police is all I can do.

If yes, Why 1b, 2b are wrong, Could you help me explain a bit ?

1b and 2b should be:
All I can do is call the police.
What we do is pack the final products.

The -ing form is used when the reversed form only, as seen in your examples. (Incidentally, those forms are not very natural sounding to a native English speaker).

Thank you Beeesneees .