I have done fullscreen before with higher than ZC 2.10 no problems but I forgot how.
Here is ag.cfg
[ZCL] zcres2=0 zcfullscreen=1 zcvsync=1 zqfullscreen=0 zcres3=0 zcres1=1 zcfast=0 quickload=0 zcnosound=0 zqnosound=0 multiple_instances=1 [zquest] vsync=1 snapshot_format=3 animation_on=1 save_paths=1 gui_colorset=0 fullscreen=1 scale=4 small=0 showfps=1 mouse_scroll=1 show_misalignments=1 combo_brush=0 enable_tooltips=1 float_brush=0 cycle_on=1 invalid_static=0 uncompressed_auto_saves=1 tile_protection=1 rulesetdialog=1 open_last_quest=1 open_last_quest=1 open_last_quest=0 open_last_quest=1 overwrite_prevention=0 open_last_quest=1 open_last_quest=1 open_last_quest=1 auto_backup_retention=0 auto_save_retention=10 auto_save_interval=5 zq_win_proc_fix=0 showinfo=0 show_grid=0 grid_color=15 brush_position=0 scale_large=1 showffscripts=1 showsquares=1 import_map_bias=0 keyboard_repeat_delay=300 keyboard_repeat_rate=80 zqmusic_bufsz=64 layer_mask=65535 normal_duplicate_action=2 horizontal_duplicate_action=0 vertical_duplicate_action=0 both_duplicate_action=0 leech_update=500 leech_update_tiles=1 only_check_new_tiles_for_duplicates=0 command01=150 command02=0 command03=0 command04=0 command05=0 command06=0 command07=0 command08=0 fps=60 frameskip=0 force_exit=0 beta_warning=!~JC~Q&% [zeldadx] heart_beep=1 use_sfx_dat=0 snapshot_format=3 gui_colorset=0 showfps=0 title=2 name_entry_mode=0 throttlefps=1 use_dwm_flush=0 zc_win_proc_fix=0 joystick_index=0 js_stick_1_x_stick=0 js_stick_1_x_axis=0 js_stick_1_x_offset=0 js_stick_1_y_stick=0 js_stick_1_y_axis=1 js_stick_1_y_offset=0 js_stick_2_x_stick=1 js_stick_2_x_axis=0 js_stick_2_x_offset=0 js_stick_2_y_stick=1 js_stick_2_y_axis=1 js_stick_2_y_offset=0 analog_movement=1 key_a=26 key_b=24 key_s=67 key_l=1 key_r=19 key_p=75 key_ex1=17 key_ex2=23 key_ex3=5 key_ex4=18 key_up=84 key_down=85 key_left=82 key_right=83 btn_a=2 btn_b=1 btn_s=10 btn_m=9 btn_l=5 btn_r=6 btn_p=12 btn_ex1=7 btn_ex2=8 btn_ex3=4 btn_ex4=3 btn_up=13 btn_down=14 btn_left=15 btn_right=16 digi=248 midi=255 sfx=248 emusic=248 pan=1 zcmusic_bufsz=64 volkeys=0 vsync=0 translayers=1 fastquit=0 clicktofreeze=1 resx=640 resy=480 scanlines=0 load_last=3 ss_enable=1 ss_after=14 ss_speed=2 ss_density=3 fullscreen=1 doublebuffer=1 triplebuffer=0 color_depth=8 frame_rest_suggest=2 force_exit=0 debug_console=0 midi_patch_fix=0 save_indicator=0 win_qst_dir=C:\Users\DELL\Desktop\ZC_2.54\2.53_Win_Beta_10\ [graphics] disable_direct_updating=1 gfx_cardw=DXAC gfx_card=DXAC [romview-graphics] resx=640 resy=480 fullscreen=0 native=1 fps=60