He can become manager in another company as well the restrictions if only for WTD & not for manager.
And for MD he can also become a MD in another company subject to passing Unanimous resolution by board and give notice to all Directors including agenda to attend board meeting.
Act DOESN'T prohibit 2 or more MANAGER in same company.
Act prohibits Manager and MD shall not be appoint or employee same time. Either one of them should be hold office not both at a time.