Thank you it`s working :)

Equation:

L__lsubs := (8*z22l^2*(z22p^2)*(z12p^2)*((((1/4)*(r^2*m__r)+I__wsl+I__zsl)*(L^2)+(1/4)*(r^2*I__r))*(z12l^2)+L^2*eta__l*(z11l^2)*(I__zpl+I__wpl+I__zpkl))*acc_l+2*z22l^2*(z12l^2)*(r*(L^2*m__r+I__r)*acc_p+2*L^2*m__r*(-phi_dot*sin(aphi)*v_y+cos(aphi)*acc_y-phi_dot*cos(aphi)*v_x-sin(aphi)*acc_x))*(z22p^2)*r*(z12p^2))*(1/(8*z12l^2*(z22l^2)*(z12p^2)*(z22p^2)*(L^2)))+F__x[1]*r__m[1]*sin(alpha__m[1])*omega__m-F__y[1]*r__m[1]*cos(alpha__m[1])*omega__m+F__x[2]*r__m[2]*sin(alpha__m[2])*omega__m-F__y[2]*r__m[2]*cos(alpha__m[2])*omega__m+F__x[3]*r__m[3]*sin(alpha__m[3])*omega__m-F__y[3]*r__m[3]*cos(alpha__m[3])*omega__m+F__x[4]*r__m[4]*sin(alpha__m[4])*omega__m-F__y[4]*r__m[4]*cos(alpha__m[4])*omega__m+F__x[5]*r__m[5]*sin(alpha__m[5])*omega__m-F__y[5]*r__m[5]*cos(alpha__m[5])*omega__m+F__x[6]*r__m[6]*sin(alpha__m[6])*omega__m-F__y[6]*r__m[6]*cos(alpha__m[6])*omega__m+F__x[7]*r__m[7]*sin(alpha__m[7])*omega__m-F__y[7]*r__m[7]*cos(alpha__m[7])*omega__m+F__x[8]*r__m[8]*sin(alpha__m[8])*omega__m-F__y[8]*r__m[8]*cos(alpha__m[8])*omega__m+F__x[9]*r__m[9]*sin(alpha__m[9])*omega__m-F__y[9]*r__m[9]*cos(alpha__m[9])*omega__m+F__x[10]*r__m[10]*sin(alpha__m[10])*omega__m-F__y[10]*r__m[10]*cos(alpha__m[10])*omega__m+.5000000000*F__x[21]*r__m[21]*sin(alpha__m[21])*omega__m-.5000000000*F__y[21]*r__m[21]*cos(alpha__m[21])*omega__m-(-D__l*v_l+M__sl)*(z12l^2)*(z22l^2)*s_l*(1/z11l^2)*(1/z21l^2)

Simplify instruction

V__kl := simplify(solve(L__lsubs, v_l));

Simplified equation:

                    1            /          4     2      2    
V__kl := ----------------------- \M__sl z12l  z22l  s_l L  + (
             4  2          2                                  
         z12l  L  D__l z22l  s_l                              
                                                   2     2     4      
-1. I__wpl - 1. I__zpkl - 1. I__zpl) eta__l acc_l L  z21l  z11l  - 1. 

                                                2  2     2     2
  F__x[1] r__m[1] sin(alpha__m[1]) omega__m z12l  L  z11l  z21l 

                                                   2  2     2 
   + F__y[1] r__m[1] cos(alpha__m[1]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[2] r__m[2] sin(alpha__m[2]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[2] r__m[2] cos(alpha__m[2]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[3] r__m[3] sin(alpha__m[3]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[3] r__m[3] cos(alpha__m[3]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[4] r__m[4] sin(alpha__m[4]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[4] r__m[4] cos(alpha__m[4]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[5] r__m[5] sin(alpha__m[5]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[5] r__m[5] cos(alpha__m[5]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[6] r__m[6] sin(alpha__m[6]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[6] r__m[6] cos(alpha__m[6]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[7] r__m[7] sin(alpha__m[7]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[7] r__m[7] cos(alpha__m[7]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[8] r__m[8] sin(alpha__m[8]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[8] r__m[8] cos(alpha__m[8]) omega__m z12l  L  z11l  

      2                                                    2  2 
  z21l  - 1. F__x[9] r__m[9] sin(alpha__m[9]) omega__m z12l  L  

      2     2
  z11l  z21l 

                                                   2  2     2 
   + F__y[9] r__m[9] cos(alpha__m[9]) omega__m z12l  L  z11l  

      2                                                       2 
  z21l  - 1. F__x[10] r__m[10] sin(alpha__m[10]) omega__m z12l  

   2     2     2                                                
  L  z11l  z21l  + F__y[10] r__m[10] cos(alpha__m[10]) omega__m 

      2  2     2     2                                           
  z12l  L  z11l  z21l  - 0.5 F__x[21] r__m[21] sin(alpha__m[21]) 

               2  2     2     2                                  
  omega__m z12l  L  z11l  z21l  + 0.5 F__y[21] r__m[21] cos(alph\

                         2  2     2     2              
  a__m[21]) omega__m z12l  L  z11l  z21l  + (-0.5 acc_y

                                 2  2     2     2                       
   + 0.5 phi_dot v_x) m__r r z12l  L  z21l  z11l  cos(aphi) + (0.5 acc_x

                                 2  2     2     2             // 
   + 0.5 phi_dot v_y) m__r r z12l  L  z21l  z11l  sin(aphi) + \\(
                                     2
-0.25 acc_l m__r - 0.25 acc_p m__r) r 

                                   \     2  2
   + (-1. I__wsl - 1. I__zsl) acc_l/ z12l  L 

                                           2     2\     2     2\
   + (-0.25 acc_l I__r - 0.25 I__r acc_p) r  z12l / z21l  z11l /

Thank you very much - both solutions are working :)