ONE MORE TIME.

Can anyone here advise me which is best to purchase.
I record from keyboards to computer and burn from there.
In the motorhome I only want to take a keyboard and this recording device H2 or H4. the question is can I use the line out from the Keyboards, into the line in of the Zoom with out a mixer or pre amp.
Question two is can I then play the recording that is in the zoon back to the keyboard through the phones out of the zoom into th keyboards line in with out a mixer or pre amp.
Which unit would be best for this.
Thank you for your help.
BEBOP