developing vs develop

Despite the increase in competition, TNT has stayed ahead of the game by focusing on two things: (i) developing its air and, also, unique road network in and around Vietnam; and (ii) expanding its capabilities in Vietnam.

I wonder if it is possible to replace "developing " and “expanding” in the sentence above by “develop” and “expand”.

No, not with the first part of that sentence containing ‘focusing’.

I think you mean “by developing” and “by expanding”.
Why is it not “by focusing on developing,… and expanding its capabilities in Vietnam.”?

No, that is not what I mean. The ‘by’ is not required. It is fine as it is written.

‘by focusing on’ relates to two things:
by focusing on developing its air
by focusing on expanding its capabilities.

Thanks, that clears up my doubts!