Passing different content to template parts

1. Simply call the template part in each place.

<?php get_template_part('content','left'); ?>

and

<?php get_template_part('content','right'); ?>

You would then create content-left.php and content-right.php templates.

2. A different approach would be to call do_action there instead. eg.

<?php do_action('template_content_left'); ?>

This could give you an extra level of control over the content template used.
eg. in your functions.php you could use something like:

if (is_page('special')) {add_action('template_content_left','template_special_content_left');} 
else {add_action('template_content_left','template_content_left');}  

function template_special_content_left() {get_template_part('special-content','left');}
function template_content_left() {get_template_part('content','left');}

This may suit you better if you need to get the content from different places depending on the current page conditions.

EDIT custom field example, closer to needs described…

if (is_page('about-us')) {
    add_action('template_content_left','template_menu_output');
    add_action('template_content_right','template_content_output');
} 
elseif (is_page('services')) {
    add_action('template_content_left','template_services_field_left');
    add_action('template_content_right','template_services_field_right');
}

function template_menu_output() {echo "CUSTOM MENU";}
function template_content_output() {the_content();}

function template_services_field_Left() {
    global $post; echo get_post_meta($post->ID,'fieldkey1',true);
}
function template_services_field_right() {
    global $post; echo get_post_meta($post->ID,'fieldkey2',true);
}

Just replace with ACF functions for outputting the desired fields.