Have checked departure records and there are no Shimmins listed as arriving in Australia after 1891. However the following two Shimmins went to USA - possibly the one in 1892 might be your Ezra but there is only the initial E given.

Name: E SHIMMIN
Date of departure: 1 September 1892
Port of departure: Liverpool
Passenger destination port: Boston, USA
Passenger destination: Boston, USA
Date of Birth:
Age: Adult
Marital status: Single

Ship:
Official Number:
Master's name:
Steamship Line:
Where bound:
Square feet:
Registered tonnage:
Passengers on voyage:

CATALONIA
Capt Atkin
Boston, USA
14493
3093
820

Name: E SHIMMIN
Date of departure: 3 September 1898
Port of departure: Liverpool
Passenger destination port: New York, USA
Passenger destination: New York, USA
Date of Birth:
Age:
Marital status: Single

Occupation: Mech

Ship:
Official Number:
Master's name:
Steamship Line:
Where bound:
Square feet:
Registered tonnage:
Passengers on voyage:

CAMPANIA
Hye Walker
New York, USA
16867
4973
115